Ya well, that's gotta hurt. Sorry, I feel for you
These spray in liners have drawbacks and limitations just as the poly types do. With a poly liner you can just chuck the in the rocks and blocks but you can't tell what's going on underneath - rust, paint wearing off from vibration etc.
It's a trade off - the "spray on" would have to be 1/4+ thick and a lot tougher to match a poly liner for impact resistance
I'm now waiting for my LE KC and my intention is to get a rubber deck cover/mat. You may want to look into that.
How to fix that damage ? Look on the web or go see a "spray on" dealer. I can't imagine it's too difficult. Maybe just cleaning,sanding, feathering,primer and shot or two of spray liner stuff. Be good as new.
Look on the bright side- it wasn't your hood or fender!