<aside> 👉 Tips:

Watch your tone: Be firm but ingratiating.
It can be painful to be ingratiating — or even civil — to someone who has wronged us, but remember that the ultimate goal here is to retrieve your prized possession. This person has that item, and whether we like or not, they have it, which means you’re asking them for something.
“The best fighter is never angry.” - Lao Tzu

</aside>

Talking Points

This is my <number> request that you return my <object>. I made my first request <in writing/verbally> on <date>, <date>, and <date>.
As you know, <object> is precious to me because <why you want it/why it is yours>.
I’m sure you did not intend to borrow it without asking, but regardless of how it came into your possession, I would like it back.
You can <send it/drop it off/leave it for pickup> - whatever method will increase your chances of returning it.
Truly, my only interest at this point is to get my <object> back. If we could make that happen, I’m hopeful we could both walk away without more hurt feelings.

Further Reading