You can't search for comments easily, but you can look up your specific comments.
If you go to your user profile (click your name at the top, or on your user card), there is an activity tab among all of the other tabs on that page (summary is the default tab). Selecting the activity tab will give you a list of all the actions you have taken on a site, with links to the respective posts.
Once you are looking at the actions tab, you can filter again by action type - in this case, you want to look at your comments. Then, you'll see a list of all the comments you've made. If the question you're looking for doesn't show up on this list, then that topic was probably deleted.