From whom did you buy the ticket? Was it unusually cheap, or did it require the [part] conversion of some form of loyalty points or the intervention of some form of third party to obtain the ticket? You should probably query them. Or was the ticket given as a prize or some kind of compensation?

I have, in the past, seen (Economy) super promo fares that clearly book into non-mileage earning fare classes offered on Etihad's own site. I cannot verify that similar offers in business cabins are not made.

If you bought this using miles/cash from some sort of consolidator or online agency, you may have been travelling on some kind of award ticket, group travel ticket, or some other kind of ticket ineligible for mileage earning, regardless of which cabin you travelled in.

Korean Airlines certainly considers S to be a non-earning ticket. As does UIA:

S is never shown when I query availability on EY flights on ExpertFlyer, so it is some non-standard code that does not seem to be generally available for "normal" sale. The clue is surely in how you acquired the ticket. The fare class should be derivable from your e-Ticket. What does the confirmation you received at the time of booking say?