I'm no expert on this, but if they are the stock Scenes from HTC, I am assuming you can download them again. Just had a look at mine, and there is an option to 'Get More'. I assume that you are offered to download scenes that are not already on the phone.
if they are ones you have made, unless they have been backed up somewhere, then I suspect you will probably won't be able to get them back, unless again you have them saved somewhere on a PC or SD card.
hat's all about I know - or don't know as the case may be.
Good luck though.
