First, I suggest you contact Fuji and/or Dwayne's to verify that they no longer process 120 film. It could have been an error that your film was returned to you.
Second, there are other alternatives for E-6 processing.
B&H offers 120 E-6 film processing mailers from A&I and Kodak in addition to Fuji. I'm sure there are non-prepaid mail-order outfits, too, but I don't have any specific references. A Web search would probably turn them up. Local drug stores, supermarkets, etc. also offer send-out E-6 processing, although it's usually not prominently advertised. You could even do your own, although of course that'll take more of your time. Of course, you might not like the quality from some of these outfits, but they
are available.
Finally, if you've got a significant stock of mailers and it turns out they're no longer of use to you, you could always sell them on eBay, on Craigs List, or in the classifieds here. When I switched to doing my own E-6, I sold a few Fuji mailers that I already had on eBay. IIRC, I got slightly more than I'd paid for them, although with shipping costs I might have taken a modest loss.