Originally, my Sails/Mongo was storing the ObjectID in the database as follows:
\"_id\" : ObjectId(\"557077fb836bdee256004232\")
Not sure what
Answering my own question!
Seemed to be something goofy happening with the brew installation of MongoDB. Manually re-installing it from http://docs.mongodb.org/manual/tutorial/install-mongodb-on-os-x/ and then restoring my backed up database seemed to do the trick.
I'd still love to know from a from a code/technical standpoint why my environment suddenly decided to start returning the 12-byt BSON ObjectID rather than the Hexadecimal ObjectID... but until then hopefully a simple manual re-install will help others who come across this strange issue!