I expect this was caused by good old "chain suck" where the chain sticks to the ring at the bottom and is drawn UP causing it to jam between the chain ring and chain stay. often caused by the rear mech tension being too high combined with worn rings and chain but can happen to anyone

A chain catcher is designed to prevent the chain being thrown off of the top of the small ring and falling DOWN. The catcher will simply guide the chain back on to the ring. This is what Schleck needed in the TDF to prevent his chain coming off.

A chain catcher wont prevent or do anything at all for chain suck. It is quite hard to drop a chain and get it jammed between the chain stay unless you back pedal after it is dropped.

Therefore if you want to avoid "doing a Schleck" buiy a chain catcher. If you want the best chance of avoiding chain suck and damaging your frame like this, keep your chain and rings in good condition.

The rest is luck