I have stumbled across the existence of a recording of the double bass sonata. The thing is, all the evidence so far suggests that the recording is only available on Youtube!
This is despite it reportedly being a recording by Frank Reinecke, a double bass player who has made a number of commercial recordings, including of solo repertoire.
As there is no evidence that this recording can be purchased, I've decided (at the moment, at least) not to add it to the main discography entries on chamber music. Nor will I take opus 82 off the list of "unrecorded music". It was never intended that the existence of a self-made recording in a location like Youtube would count for those sorts of purposes. Having said that, this recording - which has all the appearance of professional work - does make maintaining that boundary difficult, especially when it's of a work that does not appear to be otherwise available.
The 3 videos (for 3 movements) were uploaded in February 2015, which is relatively recent. So maybe there is a chance that this will be included in an album at some date in the near future.