Does he know you've found him on there Lizzie?
Could it be that he temporarily re-activated an old account for some reason?
I re-activated my Match account a couple of weeks ago. I wanted to check when I'd started talking to the man I'm seeing, but because he's deleted/deactivated his account, then his emails have gone too.
You can't then deactivate for another 48 hours.
However, if he thinks you've found him, it might be for that reason.