In France it’s only counted as abandoned if it is more than 30 years. These guys rocked up at something like 29 years and 9 months, and because there had been a verbal agreement that they would one day collect, and my mother allowed it, she was deemed to have stolen property she was entrusted to store.
I maintain that this is a dumb (i.e. completely unreasonable) outcome for your mother.
Abandonment should be measured at the takeover of property in lieu of agreement, and a reasonable time frame for pickup agreement is on the order of days, not years.
She was actually lucky to avoid criminal charges.