Looking at the search results, an agent often has to look through several tickets to find the one he/she is looking for. When it’s not only the first two, but multiple ones or single ones in the middle of the list of results, they can get confused which tickets they have already looked at.
It would be helpful to visually display which ticket have already been opened. e.g. make every row bold, and if the ticket was clicked on, remove the bold formatting.