{file} "locked by ... pid NNN", but there is no process NNN

[djc]

With a single instance of emacs running a function of my own on a file that 
makes no use of external activities, I get the message

    ...{file} locked by AB@CDE (pid 3964): (s, q, p, ?)?

but there is no process with PID 3964 and no other emacs running.  There *is* 
another buffer open on the file under a different pathname ("~/..." vs 
"X:\..."), though I don't know how that happened, since I dragged the file from 
a Windows Explorer window to visit it.

I found myself facing this message while debugging that function, which blocked 
or looped with high CPU usage when run in batch mode on that file or a similar 
one.

The message seems wrongheaded to me, but what's the best response to the 
problem?

GNU Emacs 24.5.1 (x86_64_mingw32) of 2015-04-12 on KAEL

djc