The incident occurred between 6.30 and 6.45am on Thursday (August 12) in Eynham Avenue, when a woman knocked on the man’s door and asked if she could use his toilet.
He subsequently found his wallet was no longer where he had left it.
The woman is described as being between 20 and 40 years old, white and of average build.
Officers are making enquiries and are keen to speak to anyone who may have seen a woman in this area around between 6am and 7am on Thursday.
Police are also keen to hear from anyone who may have received a similar request in the area from someone knocking on their door.
Anyone with information should call 101, quoting the reference 44210320576.