So I found this on the Skyn website -
"SKYN condoms are rigorously tested and meet the highest in safety standards. They offer the same protection against unwanted pregnancy and STIs as regular latex condoms, while offering a natural feel."
I have no source for that - I'm assuming they did the testing they say they did.
However, any condom is only any good as long as it stays put, right?
You are not at risk for gonorrhea, chlamydia, trich or HIV as your urethra was covered the entire time.
You could be at risk for herpes, syphilis, and HPV (this is true even if the condom didn't roll down). These are transmitted via the skin, and any time your genital skin comes into contact with someone else's genital skin, and there's friction, these can transmit.
If she had no sores, your chances of herpes are low and you had no chance of syphilis. HPV is extremely infectious, but if you've had other partners, chances are really high that you've already been exposed to that, unless you've been vaccinated.
Overall, unless you get symptoms, I wouldn't worry at all.
If the condom rolls down for you a lot, it may be too small or too big. You might want to play around with sizes if it's not a one-off thing.