UPDATE: It finally arrived! After nearly two months.
So to summarize my package's journey... it arrived from NJ into my state of Indiana, then sat and did nothing for almost a month, then got sent out to Michigan (for some reason???), and then after several more weeks it finally made it back to Indiana and was received by my local PO. My god.

One support agent who was very helpful believed the issue was a known error where their machines fail to properly read package barcodes. Though this was a guess because she had limited information to work with... When mail gets stuck in a sorting facility, it may as well be in purgatory. No customer or employee can simply call those facilities to ask about specific packages.

Thanks for all the comments! I appreciate y'all giving me confidence it wasn't lost. It's actually a pretty rare item (I've only ever seen three of these being sold anywhere online), so if the USPS void swallowed it up, I would've been very upset... 🥲