BTW, I've never heard of a head gasket referred to as a head cover gasket. Is that what they told you, or are you just paraphrasing what they said?
BTW, replacing a head gasket is not a simple task on these bikes. I'd be curious as to how many hours of labor they charged to the warranty. You should have a receipt that details everything they did, including labor.
I would think that the whole engine would have to come out for a head gasket. makes no sense to just throw another gasket on there with the engine still in the bike. they need to check out what the cause is, not just stick another gasket on it.
if its warranty work request a new engine cause if you have blown 2 head gaskets a 3rd is in your future if they don't pull the motor and do the proper repairs.