hmm thats kinda odd! how he managed to do that i dont know I thought the backups were locked per phone or phonenubmers serial. Anyhow IF you have no backup at all then you have lost everything. There is software out there that can recover data on the phone that was deleted.. I would personally click restore on Itunes and restart over. You cant get back what you lost that easy and software that does recover deleted data may not allways work 100% and costs money for the software..
Lesson learned huh..