Hitting debris in the water....

This past weekend I hit something, probably a stick or log of one sort or another. Anyway, I was on my way in when I did and I was probably going about 30 mph. Made a pretty good thump. When I pulled it out of the water, I inspected the hull, drive shaft and prop. Everything looked clean, but it seemed like there was a small vibration after hitting. I've only had the boat out 2 or 3 times, and not sure if I was just hearing/feeling things from being ticked about hitting something, or if there was really a problem. If it was enough force to bend something I would think you would at least see some sort of mark, dent, etc, in the shaft. Is that right, or could something be thrown out of whack? What do you suggest doing to check it out. I am going to have the boat in the shop next week getting a tower put on, how easy (expensive) is it to have it checked out?