I'd definately call the manager/ owner of the dealership. Explain what happened and what remedy you seek.
As far as being able to check the hitch is on the ball correctly;
A. Verify the coupler and ball are the same size...ie 1 and 7/8" , 2" ,
or 2 and 5/16"
B. When you lower the coupler onto the ball, verify the yoke comes down behind the ball. CAUTION NEVER STICK YOUR FINGERS BETWEEN THE COUPLER AND BALL!!!!! You can lean down and visually see the yoke.
C. After the coupler is down on the ball and the tongue weight is on the tow vehicle set the latch to the " LOCK " position and insert the safety. ( the pin or lock that goes through that 1/4" hole on the latch.)
D. Now you can look underneath the coupler and again visually verify the yoke is behind the ball, but pulled up resonably tight to the ball. There is a nut or in some cases two below the yoke that adjust the tension of the yoke to the ball. To tight and the latch won't latch, to loose and the coupler bounces around on the ball, or worse comes off the ball.
E. Hook up the safety chains ( we've already learned how important they are, right

) and the lights. Verify the lights are working
Take your time, Don't get into a rush, check and double check. I understand being a newbie, but remember the habits you start now will stick with you.
You got off to a rough start, DON'T let it ruin this pasttime for you.
Let us know what the dealership does for you.