Unfortunately been there, done that a few weeks ago. The week before Christmas I was on my trainer and the dog and my eleven-year old were playing. They had a stuffed animal they were tossing/playing tug of war with. Somehow it got out of control, flew across the room and over the couch, and into my rear derailleur. Almost immediately all chaos erupted. The derailleur hanger broke in two, the derailleur went flying through my spokes, and the chain somehow got all twisted around and caught between the front chainring and the frame and severely chipped the paint (the bike shop said it didn't damage the underlying carbon thank goodness).
All in all -- new derailleur hangar, new chain, and the tire needed truing (thank goodness I stopped the tire quickly, luckily didn't break any spokes). It rides fine on the trainer but the cables were all chewed up and will need to be replaced before spring (I'm waiting until winter maintenance specials) and everything needs a fine adjustment anyway. Somehow my fairly new (got them in early November) Conti 4000S II tire had a huge chunk of rubber torn out so I can't even use it on the trainer because the thumping sound annoys me (I knew I should have taken if off anyway since the trainer tears it up but was hoping for some more outdoor riding) so I even had to get a new tire. Lesson learned though, I have an old tire on it now with the new tire just waiting for some spring like weather.
Two years ago, when moving my trainer we didn't get the wheel tightened up enough (husband didn't understand that you can flip a lever and turned the crank instead and I didn't realize it) and the bike actually fell out of the trainer while pedaling hard catching and breaking a bunch of spokes. My bike guys now tease me that indoors is much more dangerous for my bike that outdoor traffic.