The physics were the problem  

This sounds scary. Axe doesn't have the ability to write to flash in the first place IIRC. Maybe you accidentally ran a B_Call that did? If you have this happening again, I think this might be a good discussion to start in the Axe forum: how to avoid accidentally writing to Flash. I hope you can recover most lost progress. :S

I'm not sure.

I'm not too sure I can find the similarity between Scribblenauts and that Powder game. 

If you can get Calcsys or any other hex editor to edit the VAT on your calc, you should be able to unhide it relatively easily (I think) Hiding occurs when a program name has invalid characters in it that aren't numbers or letters: Mirage/DCS hides programs by changing the hex value first character of the name by 32 (hex 20).

Unless something different/more serious is going on (which would be bad and weird)

If your stuff is all backed up, there is one fool-proof (unless you corrupted the OS, or overwrote it ) method to fixing it. Take out all the batteries, including the backup, for at least 6 hours. It really works.

I'm just putting it on hold till I feel like programming anything for my calc. This was the first game I ever tried to find on TI-calc and I was rather disappointed that no one had ever done it. So, unless another Powder comes out in the next week, I'm not giving up. In any case, I gave a large portion of my code to Scout for his mouse routine. That will save me quite some time.

On a side note, I think I just figured out how to implement the greyscale very efficiently.

My lack of interest is mostly due to being annoyingly sick and not wanting to think very much 

That was actually the only memory clear I've had in a long time.  When I start to mess with stuff that I don't fully understand (such as lists), I tend to get memory clears.

Sorry to hear that, looked good. One game you might want to look at is hell-of-falling sand. it's like the ones listed already, but minus wind, and stuff. Just gravity and etc.