Is this a result of inferior extraverted sensing?

Hello, I've posted here a couple times. I have INTJ moments, but I concluded that I primarily lean toward INFJ. 

I noticed that INTJ's extraverted sensing function is (like the INFJ) also inferior, so maybe you can help me to understand this experience I had recently (as it's shown to be a pattern in my life in various ways). 

I woke up around midnight feeling hungry a couple nights ago, so I went to the kitchen to look for something to eat. Being that I wasn't satisfied with the contents of the fridge, I drove to the nearest 24-hour Safeway at 2am. 

I walked in, picked up some milk, English muffins, & brownies. The store was nearly empty, so there was no one available to ring me up at the cash register. 

I found the nearest employee stocking items on the shelf, and she came over to ring up my items. I noticed she moved quickly, was cheerful, but didn't engage me. She had blue & pink streaks of color in her black hair, brightly colored manicured nails, a nose piercing, and some other facial piercing. I thought it was odd that she seemed so cheerful at 2am, but then I figured that she was probably more a routine night person. 

A couple in what looked like their 30's, came up behind me with some grocery items. They were wearing t-shirts, so I figured they were recently at home lounging around. I myself was quiet, serious, and observant (I was not tired, but I was hungry). 

Upon the arrival of this couple, the cashier girl picked up the, what's it called, walkie thing at grocery stores (where when you talk into it, whatever you say can be heard on speakers all over the store? the way an employee might locate a kid's missing mother in the grocery store. I'm must going to call it a "walkie-thing-which-communicates-to-all-speakers-in-the-store"). 

So upon the arrival of this couple, the cashier girl picked up the "walkie-thing-which-communicates-to-all-speakers-in-the-store", briefly spoke into it, then continued finishing up my transaction on her cash register. The couple behind me immediately laughed at this, and even though I knew the couple was laughing at what the cashier girl had said over the speakers, I couldn't figure out what cashier girl had said over the "walkie-thing-which-communicates-to-all-speakers-in-the-store" (even though I also plainly, and clearly, heard it).

My first thought was, 'Okay, this is one of my oblivious moments.' I tried to calm myself from self-criticism, and was able to recall what was funny.

The cashier girl had said, jokingly, "Hurry up and buy!" and hung the "walkie-thing-which-communicates-to-all-speakers-in-the-store" back up (implying in a humorous way that if there are other shoppers in the store this particular 2am morning, there's now a cashier at one of the cash registers). 

I only got around to laughing at the realization of this humor, a full three minutes or so later, when I was already walking out the door. The couple behind me however had laughed, immediately. 

Here are my theories about why this happened (with me): I think I shut down in terms of processing external information when I become intimidated by my ability (or lack of) to interpret the information, in addition to not trusting my own judgments & perceptions. I believe that if I learn to stop being intimidated by information, trust myself through my own perceptions & increased confidence to be able to interpret the information, that I will be able to do so with more ease.

But then I started to wonder if it was related to mbti. Was this a result of inferior extraverted sensing? Or just that I have slow processing speed? I'm slower with interpreting information which is incomplete, implied, and where context is crucial (informal jokes & clever quips & such), but with these same people who are quick to interpret informal quips: I tend to lose them when I clearly & concisely make intellectual or philosophical observations. 

What's going on, here? 

Also, I have a hard time believing that INTJ's are inferior in extraverted sensing. I don't know if it's just an illusion that I'm perceiving, but you guys seem great with piecing together informal quips based on context (and even quickly realizing where it does & doesn't make sense), but you also seem good with intellectual or philosophical observations. At least, those of you here in this community (I've been surprised as of late to meet some judgmental, overly quick thinking INTJ's who come to some really off-base conclusions). 

Some other ideas I've had about remedy-ing this for myself is: confidence in myself, trusting my perceptions, and being okay with taking it slow (as it's better to have a solid base in my perception rather than getting ahead of myself. I.e. a baby doesn't walk before it develops his/her muscles & bones properly). 

I appreciate your thoughts, thanks.

-Sue