We once had a situation very similar to your's.
A. The similarities...We were with a single male who was young, hot-bodied and well-hung. I was taking a break while he was working his magic on Teresa. I heard her scream "What was that"? It turned out that he had given her her first squirting orgasm.
B. The differences...Instead of feeling left out or jealous that he had given her something I never had, I demanded to be shown how to do it and we proceeded to wear her out, again and again
Conclusion: There is no reason to feel hurt. Sometimes the timing is right or the other may know a trick or skill that you don't. It's just an opportunity to learn something new. Enjoy the pleasure that your partner is getting.
Ted