This has shown up here as a new thread, so not sure where it's been all the time!
You are correct in your knowledge of use of the image.
Some places ask that you do indicate the source of your ref. if it is not your own - if you don't know the name of the person at such a time, then it should be OK to say the member's WC name and the RIL.
e.g one of the sites I show work on asks for such information - all I say is "Painted froma reference supplied by ....... to the Reference Image Library of WetCanvas". - if you don't know the real name, there's not much else to be done ........ and if others wished to check the original, they could always look it up here