1 - GET THEM OFF OF THOSE HANGERS IMMEDIATELY! There is nothing worse for a sweater, the weight of the garment will stretch the neck and it will become unwearable.
2 - EBay seems logical, although few people on eBay will know or care what Muse's was. There may be a Facebook group for the company, I haven't checked. Could be maintained by former customers (probably too old a base to spend much time on FB) or former employees.
Alpaca, you say? Photos appear to support this. An unusual fiber for sweaters.
I worked at Muses for many years. The price tag, which looks like a Muse's tag, will indicate when the garment was new. It had two numbers at the top, a department and a season. I don't remember the departments but season was F1 or S1 for fall or spring of a year ending in 1. Current season (if there was one) would be F6. Company folded before 1992 so my guess is number would indicate late 80s or early 90s. It only had a single digit since clothing wouldn't be kept in inventory for more than a year.
I'd be interested in one for sentimental value if you don't want an exorbitant price. Looks like only grey or tan in the box.
How they got tagged then back in possession of the vendor is also curious. My guess is the vendor took them back in lieu of payment. Not strictly legal in a bankruptcy but nobody would notice in the chaos.