I understand your frustration ~ just give it some time!
Hi there,
I had a similar thing happen with my girl. The door at my place doesn't latch unless you pull it all the way shut (it doesn't just shut closed by itself like some other screen-type doors do), and she bolted out the door. I was in hysterics, and bolted out after her, only to fall right down on my knee on the concrete.

Wasn't funny then but it is now!!

Anyway, I drove around the neighborhood and found her sniffing around after about 15 minutes. I ended up crying my eyes out over the dog & my hurt knee. I still can't bend down all the way. We have to remember to latch the door EVERY TIME we go in/out. Greta just wants to be right in the middle of where we are, so we must make sure when we go out or come in, it's all the way shut.
Just remember, your dog is in a strange place with strange people. How old is the pup? We adopted Greta (not as a puppy) and it took her a while to realize who we were. We always practice her recall (even though it still leaves a lot to be desired), and reward her like crazy when she comes. Just remember to do it when you really don't need the dog for anything. Just call them & then treat/praise them when they come. They will soon realize that coming to you is a good thing.
Just give it some time and it will get better! I know it is hard to be patient sometimes, but it is well worth it. Good luck to you.
Erin