I'm not a lawyer, but the case seems quite a bit stronger than that.
The National Archives knows specifically much of what's missing. They know Trump and Trump sycophants were the last ones to handle the documents. DOJ had inside info that gave them probable cause to search Trump's residence. The search found some of these missing documents, but there are more still missing. Some of these documents are national security threats.
For all subsequent search warrants, they can conclusively show that Trump stole documents, lied about it, and tried to hide them. They can also show that Trump/sycophants were the last person to handle documents that are still missing.
Apply that same fact pattern to a normal person. While searching the suspect's house, the FBI finds some of the missing documents. DOJ can show a judge there are still missing documents the defendant almost certainly possesses. They are going to get a warrant for any other houses, or storage units the person owns/rents as well, until they recover all of the documents. They won't have to have a witness saying I saw them put the documents in their storage unit.
Just because Trump doesn't spend much time somewhere, doesn't mean he doesn't store stolen classified documents there. There are more documents out there and they continue to be a grave national security threat. Recovering as many of them as possible is worth the candle.