I have a motherboard with an AM2 socket. Recently I bought a new processor from Amazon which is AM2+. The new processor seemed to fit into the socket so I plugged it in but I wouldn't boot. Then I did some research and found out that I got the wrong processor. How do I know if the processor was damaged?
The wiki article on AM2+ suggests that the socket is designed for interoperation with AM2 processors. While your AM2+ CPU would likely not function in an AM2 mobo, it seems highly unlikely that you could have damaged the CPU.
I haven't dealt with this stuff in a loooooong time, but for well over a decade, if a CPU fit into a socket without a hammer, it would not be damaged at power-on (even if it wasn't compatible). Socket 939 and Socket 940 were essentially the same, but one was for server-grade CPUs and one was for consumer-grade CPUs. They were almost pin-compatible, but not quite -- hence the very slightly different socket.
There might have been a couple of exceptions to this, but by-and-large it was the case.
So, if that holds true today (big if, granted), your CPU should be fine.
Sorry I can't be of more assistance with this.