I'm not sure how you could contact the other buyer as I'm not sure how you would find out who that is. The listing agent can't reveal that information to you....
You can submit a back up offer but (at least in AZ) if it is under contract then the seller legally can't cancel another offer to go with yours even if it's better. How long has it been pending? Has your Realtor inquired of the listing agent about how solid the offer is? There's always the possibility that it might not work but I'd caution you against getting your hopes up.
Best of luck in finding a great home!
With Your Success in Mind,
Keller Williams Integrity First Realty