Hi - my name is XXXXX XXXXX I'm an Intellectual Property litigation attorney. Thanks for your question.
Getty Images is notorious for doing things like this. Ultimately, the burden is on Getty to prove that you actually used this image on your website, and if they can't prove this - - which they should not be able to if you never used it - - then you should be ok legally speaking.
However, this doesn't mean that you won't be sued as you can't stop that unless you pay Getty some amount of money (usually, they will accept far less than the demanded amount). But, if you don't settle and they sue, you have a right to demand strict proof of their claim and the judge will hold them to that standard. If they can't prove their case, then you obviously would win.
At this juncture, you can ask Getty for strict proof that this image was ever on your website - - like a screen shot, etc. If they can't produce something, then their case is pretty weak. Also, it isn't usual (in my experience) for them to actually sue because of the cost involved. It's more of a bluff game.