You are NOT alone. Some jackass ended up putting red loctite at the factory on the left side panel and i had to drill it out last year (curiously the right panel had no loctite and came out just fine). This isn't a bug, it is a feature.
Next time use the dealer...and I say that because I ended up heating the left side, using the hair dryer, the works...and it did nothing. Very frustrating.
I did the same thing, rounded off the allen hole in the bolt head. I ended up getting help removing it using a screw extractor and then filed a slot in the bolt head effectively making it a flathead bolt for future use. There was red loctite on the threads as others have mentioned. Why?!?! Anyways you can probably get it out using a screw extractor and being very very careful.
Use a drill bit slightly larger than the hole you have rounded out. Drill into the head slowly and gently and after about 3-5 mm deep, the head will come off.
Remove the side panel and unscrew the remaining thread/bolt whether Locking Vicegrip.