Despite half a dozen dungeon runs on small worlds I have still found no heart statues. I however have a few bunny and bird statues, so I have a plan for next boss fight to set these up on a 3 sec timer in my arena and the spawned bunnys and bird will die during the fight ( oh the horror). I am hoping that as my health will likely not be at max that they will drop hearts that I can then pick up to avoid dying during potion sickness. I am yet to test. Will update on how it goes.
Ok after some testing, as suspected bunnys and birds will not drop hearts under any circumstances. I did this test mostly because of this line in the wikia under Heart topic 'A Heart is an item occasionally dropped from defeated monsters' the monsters page includes lots of monsters including bunnys and birds. I think I will edit it to say 'A Heart is an item occasionally dropped from some defeated monsters'. I tested with crabs and these do certainly drop hearts and mana stars if you are low on these when the crabs die. So I set up a small test wire machine that spawns crabs and kills them, looks like there is a limit to 3 of each heart or star being created in the one close area. Also the monsters page does not list any ocean monsters so looks like that needs an edit too.