When i search for something
and go to an item
and open its location from the info panel
and go back back back to search results list
Then search field/main nav bar has disappeared
Is this happening on any search or only searches from the Home screen?
On iPad or iPhone? Just tried it here and it worked just as expected. Is it reproducible?
I could reproduce it on DTTG 2.7.3, iphone 7, iOS 12.4.1, yet it does not happen all the time 
I do search from the main screen.
Sorry I don’t know how to better help you.
And did it just appear with 2.7.3 or was it also there in earlier versions? Because: We haven’t changed anything here that (out of the top of my head) could be related.
I am pretty sure it was there on 2.7.2.
Ok try this:
search from main screen
open a pdf result
go back
see if the top bar disappeared
if not click on other pdf until it does