Well I think it would be a good idea. :/
Think about it this way, Zoroarks are usually very secretive and can change into other Pokemon, thus if some were in the Hoenn region no one would know, as with Unova. The mother had an egg in the Hoenn region while in the forest, and tried to escort it to a safer, different location, disguising herself a Mightyena to put fear into the usual pokemon of the forest and thinking she could remain undetected by the camp.
Obviously, her scent tipped her off, and she was attacked (much like Ambrose.) She was killed, and the Mightyenas couldn't eat the egg she had. So, why not take it back and wait for it to hatch, and then have a snack?
Is that a neat enough backstory to explain? The mother's scent is also imprinted on the egg, so that could add on a "Daddy, where's mommy?" curiosity that can be discovered later on when Ambrose gets back from Kyogre.