Is it possible that I don't have a hymen?

Okay, so I am a 13 year old girl and a virgin. I have never had a period, but since I'm going to camp this summer, I needed to practice inserting tampons. (Note: I took them out right away, don't worry.) Anyway, I familiarized myself with my by looking in a mirror. I saw on a medical website that the hymen covers part of the outside of the . Like a piece of saran (thin plastic) wrap over part of a pringles can. I sat on the counter and took a look and I just saw a hole! I know it was my . I play volleyball and basketball and do track. I ride my bike at least 10 miles a week, too. Is it possible that the hymen can go away without having ? I put the tampon in with no problems by the way. And it was my first time inserting a tampon! All my friends (we're really close) said they had trouble getting around their hymens, but I don't believe I even have one!... AGHHHHH!