I went into the thieves guild a while ago and the floor completely disappeared and you could fall straight through why did this this happen.

Also when I exited and entered once more the glitch was gone!

It just failed to load the cell properly. It happens because the game is so big.

I have found that that does happen but It really didn't look like a patch/cell that didn't load.

I wish they could fix those glitchs!!!

You're 99 years old! I don't expect you see a patch in your lifetime.

Don't worry I have a life span of 99,999 years.