Happens using Chrome on the Nexus 7.
Viewing “What’s New”, select numerous threads in new tab, tap on a tab and sometimes tab closes.
There is no “Ctrl-Shft-T” available to reopen last closed tabs, cannot select “Quick Links” to get latest posts and because the thread has been opened it will no longer show in the “What’s New”.
Yeah, that annoys the heck out of me. You can also try Unanswered Threads, if it’s unanswered, or, if you remember what forum the thread was in, go to that forum to see it again.
If you’ve finished looking at new threads, then mark all as read and immediately go back to What’s New. It should then say something along the lines of “No new threads, click here for all threads in the last 24 hours”, and you might be able to find it that way.
Many thanks, works a treat 
Meanwhile I managed another solution…
'desktop, copied and pasted the “Quick Links->Today’s Posts” link, to Dropbox…
'Nexus 7, Chrome bookmarked the link.
How/where do you do that? I don’t see that option anywhere.
The dropdown box which is NOT affected by the Search Box:
“Forums Actions->Marks Forums Read”
Ah, thanks.