Likelyhood anal cancer would be missed in 34yr male after normal colonoscopy 1yr ago? (not even hemorrhoids seen at time of test) have them now tho.

Unlikely: It is unlikely that you have anal cancer, but to be safe you should inform your primary care physician about your symptoms and undergo a physical examination.

Not big problem.: Although hemorrhoids are an issue that can lead to anal cancer, they need to be very severe and longstanding and associated with a mass. Someone your age with a clear colonoscopy is still likely in the very low risk category for this cancer unless there is family history.