I would expect him to have cleaned it.
Or just disposed of it entirely.
Could have chucked it into the sea on his way back before having a burger with the teenagers camped out.
The scratch he could do nothing about.
He could have noticed the paint, blood on the outside and grey hair. Depends how dark it was.
Decided to just put it back in it's box at the back of the gun cupboard.
Was not expecting the relatives to be suspicious & get access to WHF to snoop.