I really need to know how do you save something that you made or worked on?

The other day I put a lot of time into a model,went to save it not as a scene but as a obp.Then went back the next go round guess what not to be found!

The mat file's were in there slot's but no model.I mean people show up here all the time with free model's in obp or obj file.

It was a wast of eleven hr's work.

I just must be missing something or other? :)