TIFU by trying to make my fiancee's favorite dish

I'm so embarrassed and it's been two days. So my fiancee's favorite dish is pasta ala vodka. The important context is I (21) live in the US where the drinking age is 21. My fiancee is 19. Okay?

I've never bought alcohol before, and my fiancee obviously can't buy vodka, so she can't make it. So I said I'd buy the stuff so I can make it for her, since she's been having a stressful time in college and has been eating canned soup and ramen in her dorm. It's her favorite food after all and since she's not at home nobody else can make it and it's too expensive to go out somewhere to buy it.

So whenever we're together for the weekend I try to make her good food. Keep in mind, all the alcohol in the vodka burns off in cooking of course! It just adds to the flavor. And I'm a pretty good cook, so I'm confident I can make it well.

So we're out at the grocery store, buying all the stuff for the sauce, the noodles, but I realize the store only sells beer and wine, not vodka. So we buy the other stuff, get in the car and I get directions to the liquor store.

I'd like to stress, again, I've never bought alcohol. I've been into a liquor store with my grandparents before, to help them carry stuff when I was around 19 or 20, but I've never bought anything. I'm on too many medications to be able to drink despite being 21.

So, when my fiancee asks if she should wait in the car because she's not 21 I shrug and say "I've been in a liquor store with my grandparents before I was 21 and nobody cared." so she goes with me into the store.

We kinda walk around a bit but all the bottles are too big, we need like, a 1/4th cup worth of vodka and since I don't drink and even if she was old enough she couldn't drink either (different medication but similar reasons), so we don't want to have to have a lot of vodka left over.

So around the checkout I notice the tiny bottles and immediately gravitate towards them, examining the bottle and trying to find out how many mL is in a 1/4th cup while the cashier stands over to the side kind of looking at me funny.

I tell her this is the just right size for it, then I go over to the register and set the bottle down, and fumble for my license. I have social anxiety so my hands were already shaking.

The guy at the register is a big guy with a beard, and he angrily goes, "licenses?"

I stutter out something along the lines of "I'm just buying it-" and he goes "I need ID from both of you if you're buying for her." and my face probably turns entirely red I'm so embarrassed, I didn't think of that, so instead of trying to explain I'm just trying to make dinner i mumble out some sort of apology and leave the store with my fiancee following behind and she's saying "I told you!"

The whole time I was paranoid I was gonna get arrested for "attempting to provide a drink for someone under 21", so I just sort of drove away. I still feel like a wanted criminal after two days.

We ended up going to a different store, and yes she waited in the car, and yes I got the smallest bottle they had and made dinner and it was good and no actual alcoholic drinks were consumed.

I'm just so embarrassed. I keep sitting here thinking about it like laying awake at night so I figured I might as well absolve myself by posting it.

TL;DR: I'm 21, my fiancee is 19, I tried to buy vodka (for the first time ever) for making pasta ala vodka for her, a dish cooked with alcohol that burns off, but the cashier at the liquor store thought I was trying to buy her vodka because she came into the store with me (and I got scared I would go to jail)

Edit: thanks guys for already reassuring me it wasn't a big deal. my anxiety disorder honestly gets the better of me sometimes