The man had a working key for the room, and also a note purporting to be from the supposed victim giving permission for him to enter the room.
"The story and the fact he had a key made the receptionist let his guard down," Nolan said.
The motel worker walked the man to the room before returning to reception.
"The guy then moved his car next to the room, unloaded the guests' stuff into his car - everything, as far as we know."
A cleaner later entered the room and, presuming the guests had checked out, carried out a full clean.
"So when the guests came back they came into a completely clean room with everything gone," Nolan said. "They were obviously horrified."
Nolan acknowledged that situation had been handled poorly by the motel. The receptionist should have asked what the name of the woman staying in the room was, but didn't, he said.
"And we have issued two keys to a guest at some point and only gotten one back and we've not correctly handled that situation because our standard procedure is if somebody says a key's lost ... we need to change the lock."
Nolan said the motel would compensate the guests for everything they had lost.
Active Detective Senior Sergeant Will Loughrin said there had been other burglaries of motels in the Hamilton region recently.
"We're looking into the possibility of whether they're linked," he said.
Loughrin said the items that were stolen included clothes, iPads, jewellery, and journals which documented the lives of the couple's two daughters. These were intended to be given to them as 21st gifts.
"We're making inquiries as to who this male is and we're working with the motel and the Motel Association in terms of giving them prevention advice to keep themselves and their clients safe from burglaries."
The motel did have CCTV footage which police were examining.
Anyone with information was asked to contact Hamilton police on (07) 858 6200. Information can also be left anonymously via Crimestoppers on 0800 555 111.