I don't know about your mechanic, but...
I have been know to leave the odd nut, bolt or screw on a "friends" workbench or on the floor near the car or motorcycle. Drives 'em nutty, it does.
I few dribbles of hydraulic fluid below my hangar buddy's main gear was always good for a laugh when a group of friends were visiting.
"WTF! Monte, is that you, again?"
I know of no cable nor wiring bracket that bolts to the R65 fuel tank...