Just to be clear it did give an indication at the start that it was re-indexing, just there was not progress bar or “completed” status.
Just try it anyway, pretty pleeeease 
(I have just synced my test database to my iPad to play with this; I used exactly the same Finder Comment as you did - and it is found approx. 0.5 to 1 s after I press search. I have tried using the whole comment, parts of the comment, capitals, it works.)
I assume from your screenshots that you are using DTTG 3.3?
Closed and still no joy. But now I see a countdown of indexing items on the “home page” it’s at 758,000 so I’ll let you know in a while
I thought you might 
Thumbs pressed, but this should be the solution. If it is, please don’t ask why - I’ve already got a headache 
Glad to tell you no headache - it worked. The strange thing is why all three of my iOS and iPad devices the index failed but the two Macs were ok???
You’re welcome.
No, that’s the bit with the headache - I can’t answer that question. Two different pieces of software with two different mechanisms - but why one failed and the other did not, well I don’t know. I’ll ask the lizard though.
as I mentioned above, I can reproduce the ‚missing index‘ issue easily when one or more of my sync stores are offline.