That is the whole point of why the anti-rootkit scan alerted on a ‘suspicious’ hidden process, e.g. when you go looking for it in explorer, even with show hidden files and folders you can’t find it in the reported location. Had you been able to find it and actually sending the file for analysis wouldn’t really have helped as it wasn’t the physical file, but the circumstances of it being hidden in this way that caused the alert.
Why UHPclean needs to operate in this way is beyond me, but obviously it has done so for many years. Along comes an update in the anti-rootkit scan (or change to its sensitivity) and it is flagging what was in the past left unmolested.
The detection was corrected yesterday so it shouldn’t be being detected now as you found.