Thank you for your post.
I am unable to replicate the issue. I have a file with more than 884 scripts, and when I go into Manage Scripts, and search for A, all entries that contain an "A" are displayed. If I type in No, I immediately get all scripts that contain "No".
I am using FileMaker Pro 13.0v1 under Windows 7.
If you want to send me a clone of your file, I will try it here. Check your Inbox at the top of this page for instructions where to send the file.