The sheets feature is having issues and difficulty with the search function when looking for hypen text strings for example ST-05. Here is the response from Forma support:
I can confirm that the efficacy of that search function is directly related to the type of file you are viewing. On a text PDF file it found hyphenated words and phrases immediately and anything else I could throw at it.
For drawings, the curved/angled text and a lot of the larger title-like text was not captured by the file/sheet search function. This is a limitation of this feature currently.