...can someone please help?

I came over to the US on a K-3, handed my paperwork into the border customs and then filed an I-485, along with an I-765.
I got my EAD through, and recently attended my AOS interview with my wife 6 months. After so much time and expense I was relieved to finally get to the interview stage, thinking the worst was behind me. Was I ever wrong. It turns out that USCIS has mixed up my file with another applicants. They have misplaced my medical forms, for a medical which I had undergone in London before I was allowed to come over. I now have to wait to see whether they can find it, or I have to go for and pay for another medical. They say 2 weeks till they let me know...

So my case i pending. They took my I-94, and stamped my passport with a pending stamp, along with my A#.

My questions are:
Has anything like this happened to anyone else?
Can I still leave the US, even though they have taken my I-94?

Thanks.

D.