The incident took place around half past five on Monday in Falkenberg.
When the man came up to the attic, the three masked people kicked, hit and threatened him.
He was robbed on his phone but should not have received any serious injuries.
The man and the woman must have decided to meet near a restaurant.
- As it sounds, she may have been some kind of decoy, says Stefan Gustafsson, the police's spokesperson.
No one has been arrested yet.