Now that I think of it, the mixed sock problem can actually be worse than O(n^2). For instance, if I decide that I want to wear my Marvin the Martian socks, and can only find one in the sock drawer, then it's a big problem. Look in the other drawers. Look under the bed. Look in the dryer. Repeat. Repeat. Until the other one is given up for lost.
It doesn't depend just on n since you aren't just searching through n available socks, you are searching k places with n_k socks in each place and with p_k confidence that you have thoroughly searched each place. I can't think of a more general problem that this might correspond to.
Now that I think of it, the mixed sock problem can actually be worse than O(n^2). For instance, if I decide that I want to wear my Marvin the Martian socks, and can only find one in the sock drawer, then it's a big problem. Look in the other drawers. Look under the bed. Look in the dryer. Repeat. Repeat. Until the other one is given up for lost.