hextech chest not stacking on loot page

A couple of days ago I had two hextech chests. I opened one which gave me another bonus hextech chest but the chests did not stack on the loot page. I thought maybe the client was bugged so I logged off and back on the chests were not stacked. I randomly choose to open one of them which left me with one chest. I just earned another chest by getting an S on a champion and the chests are still not stacking.

Does not affect gameplay so no big deal, just thought I'd let someone know. Maybe the bonus hextech chest was supposed to be a different kind of chest like a masterwork chest ;-)