Graysky's creating the dummy files (nuv and nuv.png) and then
deleting normally from frontend seemed to work, but the
_NO_TITLE_ came back (for me) the next time I deleted a
recording.

A note to others, my file's channel ID appeared to be 4294
which does not match normal files from either of my two inputs.
It turned out that it was actually 4294967295 (as in 0xffffffff)
as shown in the frontend "details". Also the seconds were 53
where the seconds on my other files are 00 (but perhaps this is
because it was a live recording).

Goofee's sql seems to have finally done the trick.

Google says that others have deleted it using this sql approach.

Thanks to all.