Dealing with non-communicative STBXH?

TLDR: How to deal with a non-communicative soon-to-be-ex-husband that has a history of ghosting?

Separated about six weeks ago. No kids. Prior to splitting, we both had storage units, I closed mine out within a month of obtaining it. My STBXH has a serious hoarding problem, so he has a huge storage unit filled to the brim. Before we split, he placed one of his personal belongings (a VERY HEAVY mechanical tool) in my storage unit. IDK how much it weighs, but it weighs more than my dog, and she's ~75 lbs. About two weeks later, we went our separate ways.

He was supposed to retrieve his mechanical tool from my storage unit about two weeks ago. On the morning of, he emailed me, and asked if we could reschedule, apparently he had some last minute things come up. I said sure, no problem, and offered him 6-8 other time-slots. He never responded to that email. I reached out again yesterday to follow up, and provided another round of 6-8 time-slots for him to retrieve his mechanical tool. He hasn't responded.

I have an autoimmune disease that affects my musculoskeletal system, so I'm unable to move it from my car trunk to my apartment for further safe-keeping until he decides he wants to pick it up. A few weeks prior to splitting, he said it belongs to a coworker of his, and apparently costs a pretty penny (~$700), so I don't want to be rude and just throw it away or whatever. But this tool is literally making me burn more gas than necessary. I drive my car daily (work, etc.), so it's making me burn gas way faster than I normally would.

He refuses to communicate via text message or phone calls. Only does emails, but barely. He's always had a history of ghosting during our marriage, so this isn't surprising. But. I just want this literal hunk of heavy metal out of my car. How can I force him to come retrieve it? At this point, should I reach back out to the mediator and essentially have her 'force his hand', so to speak? Since he seems to pick and choose which emails he does and doesn't want to answer?

Thanks in advance for any feedback.