It is a lie. First of all, the first rendition of his trip is less than two hours after that trip. How would the police know to ask him if he went to the drycleaners first thing??? Dw is going to say, "and I didn't go to the drycleaners first before taking my MH back to High Valley"?
The police specifically asked him if he went anywhere between the end of the trip and Sherman's. Particularily in the Redden interview, later that day. Westerfield had numerous opportunities to tell it and didn't. He did tell Redden about trip #2 (black clothes drop-off).
The police went to the drycleaners to get the stuff with only ticket for trip #2 stuff and the drycleaners called them the next day or so to tell them about the additional bedding and jacket.