They left no message.  I called back, it's some kind of "reward redemption center" blocked the number

They're still at it.  Same thing, never rang, called twice in a row (within moments).  No message.  I *never* call numbers back... that's a recently added trick to the scammer's bag – the return call will show up as a charge on your phone bill (like a 900 number).

For people cursing the DNCL... the DNCL can only protect you from legitimate marketers (and I'm sure it does a lot of that).  Illegal scammers use auto-dialers that simply call every possible number... 717-397-0000, 717-391-0001, -0002, -0003, and so forth.  There is no defense against this other than blocking every number you don't recognize that calls you.

What would be useful would be a database of numbers I could pre-emptively block... maybe whocallsme has an income opportunity there?  :)

Called, left no message.  Fifth call from unknown numbers in two weeks & none left any message.
Other unknown numbers are:
206-538-5464 (Seattle, WA),
307-217-4764 (Buffalo, WY),
646-650-3961 NY, NY), 646-650-3969 (NY, NY)  (Suspicious of 2 calls from same area within minutes of each other)
Do not know anyone in those areas.

There is always someone with a useless smart [***] response. Congratulations Hotdog You win todays DUMB [***] AWARD!

Same issue described.