Do not save the file from SAI, open in Photoshop to see if it is okay. If not, download IrfanView (it's free) and try to open the PSD with that. If it looks fine and everything is there, save it as a new copy and use that version. If the stuff is still missing, then there's not really anything you can do, unless you've got another recent copy of the file you can work from. Otherwise you're stuck redoing some things.