Is this still owners property

Looking for some advice re legal situation. A relative loaded a piano to her "in law" some years ago on long term lend agreement. In law split from her partner over 18 months ago but piano was never removed from house they shared at that time. My relative contacted person still living in house with a view to arranging to have piano removed from house but was told that he sold it. No apology or offer to give her the money he received for the sale of the piano. Can anyone advise where the owner of the piano stands with regard to this from a legal perspective?

Thanks

Some years = how many years? 2? 20?

Relative has it about 10 years. Given on long term loan on understanding she would return it when owner had children of their own who were old enough to start lessons.

Was there anything in writing ?

Nothing in writing. It didn't really need to be since she always intended to give it back. When relationship broke up she left it in the house and never removed it so ex partner went and sold it without permission or contacting anyone to say he was doing it. That said no attempt on anyones part to have it removed and as I said 18 months has passed...

Honestly?

Forget about it. It's over and would cost too much (financially and emotionally) to even
consider taking any steps.

mf