What R_Hatch says will work, but...
Why were you working "for a while" on a scene without saving?

One of the cardinal rules when working with Poser (and many other "not quite as stable as they'd have you believe" apps) is:

"Save Early and Save Often (under different names" (just like voting really..).
Never, ever, work on a scene for more than 1/2 an hour without saving.
Alway save immediately before making any major changes (adding a new prop/character, changing materials, stuff like that).
And always save under a new name (MyScene0, MyScene1, MyScene2 etc...)That way, if you don't the the result you wanted, or if either the prop/figure or (often more likely) Poser starts giving you problems you can just re-load the previous version (or furthur back if that is required). And if the earlier version still mucks up, exit Poser, re-start Poser and re-load the "last-good" save (exit/restart often helps 'cos Poser leaks memory)...

I can't stress it high enough: Save Early and Save Often (under different names).
It's a Must Do!

You can always get rid of he interim versions once you've done the final version....(but even then, keep a couple of "High-Point" saves around, just in case)...

Cheers,
Diolma