I learned the "never loan tools" lesson the hard way - way back in 1978.
I've mentioned my 1975 Singer Fashion Mate 252 before. It was my only machine at the time and I sewed the devil out of it.
An acquaintance, a neighbor, with a toddler, wanted to borrow it to make simple kitchen curtains. I said "yes" without giving it a second thought. After a month I had to start asking her when she would be finished. After the second month I began pestering her. She lived three doors down in a small complex of small apartments. She returned it in the third month.
The spool pin was broken. She tried to glue the stub back into the machine, and dribbled glue all across the top. It's still stuck there.
The felt pad was "lost." Her kid probably ate it.
The bobbin was "lost."
The case was dirty and sticky.
Her son had scratched the outside of the case with a metal toy truck - then he "colored" it with a red marker. She thought that was cute.
My FM still wears the battle scars from the one and only time it was loaned out.