Sperm do their best work in a warm, moist environment. Oxygen is not their primary enemy.

If there was still visibly wet pre-ejaculate (pre-cum) or semen (ejaculate, cum), on his fingers or hands and he touched your genitals and inserted his finger(s) into your vagina then you have a low risk for pregnancy. You also have a some risk for STD transmission because your genitals were essentially unprotected if he introduced his bodily fluid into you.

Next time, have a clean towel to clean hands with at a minimum. Better yet, alcohol based rub then wipe off with a clean towel. Good luck.