Residence Inn Minneapolis Downtown at The Depot by Marriott

I don't know who I can complain to about the customer service, and at this point I think I just have to accept that our things are lost. My husband and I booked three days and two nights, but a family emergency meant we had to leave on day two. In the rush we left belongings behind, and called six hours after checkout. They said the room was already cleaned and asked us to call the next day so they could check with housekeeping. The next day they found our things and said they'd mail them if I provided a label. I asked for the box dimensions and weight so I could make the label, but they kept insisting I didn't need that and should just tell the post office it was a small box weighing 3 oz. After going back and forth forever, I gave up and made a label using 8x8x8 and 3 lbs, not 3 oz, then emailed a UPS label. They replied that they were waiting for USPS to pick up the package. I panicked and explained it was UPS, then called. We argued again, with them saying the label was USPS and me explaining that UPS would deliver it to USPS near me for the final leg. We hung up, and I thought they'd understood. A week later, tracking still showed that UPS hadn't received or scanned it. When I called again, they said it would show up today or tomorrow, then told me they just knew when I asked how. I pointed out that tracking still said UPS hadn't received it, but they said I didn't know. We kept going in circles, with them insisting it would show up and giving no proof. I finally asked what to do if it didn't appear, and was told to call back. There's no point talking to people there. They don't listen and act like know-it-alls. Can someone point me to the right person to complain to?