haha the overwealming response i got from chat and posting here was "dont worry about it" im glad i did.
The bikes are fine. The fronts were securely fastened to the trailer the right way. Other people suggested i use a backstrap too. so i did.
The reason the back tire slipped off the rail coming home is these factors :
1. the backstrap only pulled the bike toward the front, not toward down.
2. Mopeds are not motorcyles nor do they weigh enough to stay down just by gravity.
3. It started to rain as i got home, and that made the wheels slide in the huge rails built for a motorcyle.
4. Coming off the freeway and down to a stop trying to get home, the weight swung forward, and the bikes went up not sideways or down. Firmly securing the back rim to the rail will prevent this happnening in the future.
All in all it was fine, the plethera of straps made it catch itself and nothing went catastrophic.