Briefly describe (1-2 sentences) the Bug you’re experiencing:
The search feature no longer finds most old, complete tasks. Newly-created tasks are found, but older, completed tasks are sometimes found and sometimes not.
Steps to reproduce:
On the mobile app, try to search for a task that was created several years ago, whether or not it was completed recently. Most of the time, it is not found, even though it exists.
Browser version:
Android app version 6.91.3
Upload screenshots below:
Hi @Tristan_Brown1, welcome to the Asana Community Forum 
This capability hasn’t been built out for the Asana mobile app just yet. We’re hoping to improve the functionality of our app in the near future and this is definitely on our radar.
That said, I’m going to move this post to #productfeedback so folks in the community can upvote it and so our developers can get a better look at the needs of our members.
In the meantime, I recommend utilising the browser or desktop versions of Asana to access our full features.
This capability worked fine in the app 3 weeks ago. It only stopped working recently.
I experience the same thing, it is frustrating not finding your information, until recently the search function on mobile worked just fine.