Pretty much everyone that I know feels like they didn't deserve their black belt, however they got it, testing or not. I know I used to feel like that. I got over it.
How about some trust in your teachers' judgement. Yes, you didn't do a grading for the belt, but it's not unthinkable that they genuinely thought that you were already on that level, and the only thing missing was actually arranging a test. Which in the circumstances might have felt a bit superfluous to the teacher.
Another thought - if I had a student who trained as much and with as much enthusiasm as you sound like you did, I might well think "well, she's this
close to the rank, I'm sure wherever she goes she's going to start training in something, so eventually she will have the skills for sure" and give the belt as indeed a parting gift, but with the confidence that in the furure, you're not going to make it look like a bad decision.
Basically, you can decide to feel resentful about it, or you can take it as a vote of confidence and decide to live up to that.