Getty purchases and/or manages the licensing of photos from professional photographers. When a photographer submits work to Getty they have to submit the work along with paperwork documenting that it is the original work of the photographer. All the images on Getty are either copyrighted by Getty (if they bought the copyright) or by the artist which has an agreement to allow Getty to license these photos under agreed conditions between Getty and the copyright holder.
Depending on the deal with the photographer they may license the image as limited use, royalty free or variations (such as the number of runs for print, non-profit usage etc).
I recommend contacting Getty for the catalog number of the image and then searching the site. If the photo you have matches, and you don't have a receipt where you have licensed the photo, then you are in violation of copyright infringement.
According to U.S. law, any original work is automatically considered copyrighted material of the creator.
On the flip side...as a photographer myself, I've had to deal with people stealing my work inadvertently. After talking with a copyright lawyer the advice he gave me was to contact the party and ask them to remove the work, if they do fine, if not, then file a civil suit. I'm of course talking about professional images (or taking a photo of Mickey Mouse and selling it on a postcard), not a snapshot of a bridge that would be so common that there is no artistic value.
So, ask yourself this:
- Did I take the photo? (and do I have the model / property release paperwork)
- Do I have a receipt or document showing that I may use this photo?
- Do I have proof showing that the photographer has put it into the public domain and licensed it free for use (and I'm abiding by those terms)?
If you answer no, then your using someone else's work without their permission.