Hey, I've been noticing this lately and it really bugs me, because I have so bad RNG...
Basically, if your LMG procs while you have HST active, if you cast Totemic Recall, your HST will be destroyed but you get no mana back. And of course, for me, LMG always procs only when there are 2 seconds left on HST. Somebody else also noticing this?
You should wait until after the LMG proc finishes to get your mana back with Totemic Recall.
I recommend casting 2 healing surges and summoning a Magma Totem, all while under the LMG proc. And after the proc finishes, cast Totemic Recall.