My baby fell off the bed and I'm PISSED

My LO is 9 months and rolled off the bed today.
My SO was supposed to be watching him.
I'm pissed because this is the SECOND time it happens and both times he was supposed to be watching the baby. I kept my baby up for an hour to see if he acted different or anything.
He cried after the fall :( and calmed down after I cuddled him for a bit. He acted normal after that, playful, smiling etc. but I'm still worried. 
There's no bump and no scratch that I've noticed but I'm still mad my SO wasn't paying close attention to him. Today it was becaus he was grabbing a diaper to change him but STILL I always keep an eye on him because I know how fast he rolls and that he doesn't sit still.
Anyone had this happen to them before?
Any tips? 
Any advice would help me relax!
TIA