There is always a possibility, but if it was placed in the code by the developers then their legitimate customers would also be effected. Believe me, as someone who customizes premium themes on a daily basis for clients.....we would know about it. The thing that would worry me more would be the source in which you obtained the theme. I have run across premium themes being given away from third-party websites that was filled with "dirty" css, nasty javascript, and encrypted footers. As long as you fix it (doesn't take more than a few minutes) it should be alright.