I found out one of my patterns on a phone case on etsy. I am almost sure it's print on demand because I do sell some phone cases and mugs myself  with my own drawings there and I see their mugs are from the same pod place.

Is it allowed to use the images for print on demand with a standard license.
The image has probably been bought on 123rf or Bigstock.

By the way how do I look for the sales of a particular image on those two sites?