The OP's code could have been in the "VIP" (as opposed to "SOS") category. This is how Choice has classified some corp/org codes that bore the 20-25% (and greater?) discounts. Sometimes these VIP codes have required a phone call to reservations. I haven't tried re this one, but someone might.

Unfortunately, as in recent experience, VIP and SOS rates have been the same, making the distinction moot. (And then the occasional disappearances altogether. Can something be more moot?) Some have speculated that this and other troubles we have are the result of the FlyerTalk Pogo Effect -- e.g., "we have met the enemy and it is us" a propos of discussion here. Some have speculated, rather, that it's the loose ChoiceHotels system, as reflected in sdsearch's many valuable analyses.