My flat bed printer/scanner/copier shows a USB tray notification as
well, but then again it also has a card reader. The op's printer may
have that feature but it may not have been why that particular printer
was purchased and thus gone unnoticed by the op. Frankly I can't recall
if any of the previous printers, one of which was 'print only' caused
the USB tray notification or not, its been too long.
But in either event, Windows normally plays a sound when a USB stick is
inserted into a USB port on the computer as well as display a pop up
windows Explorer window showing the stick as an available drive, just
minimize that window as a constant reminder that the stick is there. So
there is ample evidence that an additional USB device has been
introduced and an available way to keep it noticed. If the stick is
always present you could also put a short cut on the desk top to the
drive as an easy way to check or use it.
Of course if you turn the aural and visual cues off then you will just
have to manually check your file manager to see if an additional drive
has appeared or been present all along.
Its the way Windows is supposed to work.
John