Does it? Are their actual people named Issac? I'm asking seriously, because I've never ever seen that.
But it really doesn't matter, because even if it exists, 99% of people with that name spell it Isaac. If we had a recruit named David, I don't care if you once met a dude named Dayvid, there's no excuse for spelling it wrong.
If Ty's last name was spelling Issac, no one would fault you for spelling it Isaac, because that's the normal way, just like if I mistakenly spelled your friend Dayvind's name David. But there's no excuse for misspelling someone's name when they use the traditional spelling.