Aut, I left my old job 5 months ago and despite them saying I'd get a box to return my laptop, that never happened. I emailed HR to let them know (general hr@company) and got an automated message saying they didn't work for the company anymore. As hilarious as the thought that all HR left the company, I don't think it's particularly accurate.
So, how long until it's considered abandoned? Maybe I should charge them a storage fee to catch their attention.