I think you are absolutely correct.No, I wasn't kidding.
A welfare check is done when there's a reasonable suspicion a person in a particular house needs help or is dead. Not knowing where GP was doesn't lead to the reasonable suspicion she was at the Laundries. Police action was needed but not disguised as a welfare check to get around the need for warrants. Being scared isn't grounds for a warrantless welfare check if there's no reason to think the person is in a particular location.
JMO
But once LE figured out that it was Gabby's van sitting there at that same house, wouldn't that create a reason to think she might be there?