Hi,
Yesterday when i logged off, the timer had somewhere around 7-5 hours remaining ( it was 2 in the morning) out of 7 days. Today when i logged in the egg disappeared, no mysterious egg, no cracked egg, nothing. I read on wowhead that this might happen, if the egg was to hatch during server maintenance. Can someone confirm this? Or is this bugged?
Did you check the top of your bags? They move up to the first free slot in bags. Check your bank aswell if you held it there. They shouldn't disappear for no reason.
If your inventory was full, that may be the cause. Hatched egg is a new item in regards to mysterious egg, so it needs atleast 1 free slot for it to be stored in your inventory, therefore if your bags were full, it disappears.