Replacing single recep with duplex
I've recently encountered in a small contracting job, a T-blade single receptacle located in the dining room of an older home. The customer would like to replace the single recep with the more common duplex. After inspecting, I noticed there was no power going to the single Recep, and it had originally been wired with a three conductor. I would assume the three wire conductor was connected to a 20A breaker in the panel. As I went to check the panel, I did not see any tripped breakers. I was also very confused to find such a device inside a residential family dining room. Perhaps the room was not originally intended to be for dining, but in find this unlikely due to its location next to the kitchen. It's an older home, easily from the 60's to early 70's. Could it be that the lack of power stems from the circuit being deleted at some point through the years? I still haven't taken the cover off the panel in attempts to locate which breaker it may lead to. I did, however, inspect a receptacle right next to it, which could easily appear to be on the same circuit. This duplex was wired with just a two conductor, which removed any doubt the two were connected. Would you advise to simply jump from the duplex to a newly installed duplex, in place of the current single recep?
Thanks so much
Cheers