Broken Keepers on intake valve What that can cause

If your cylinder heads and cam are factory, then it was probably just a defective part. Keepers dont fail very often, and even less often in non race engines.

are you talking about the valve locks, if you are you best get that fixed before you drive it any unless you want a big hole in a piston and a bent valve and a bad head and cylinder

The only way I see keepers failing is if the valve has been slapped back in its seat excessively hard, they were't installed right if it was torn down at some point, or you have an aftermaket cam with too much lift for a stock setup/heads. Seeing as how you don't have any of the above, don't worry about it (unless you continue to drive with it like that. Just get a new pair of keepers and install them or what dastang2 said will certainly happen.