Hello @MarkK071 ,
It appears the search functionality on the My Campaigns tab is still an on-going project for the engineers to make work. Some customers have been able to use the search function within the Reporting tab to achieve a similarly desired effect, however this would only apply to sent email campaigns.
With that said, I've gone ahead and tracked the relevant service requests, and passed your info to the engineers for further review. If and when there's an update to this functionality, they'll make sure to notify you.