I wonder why noone has mentioned it till now...
We can see the 4 hours countdown bar on top of the creepvine statue, but when it reaches to zero there is no "Collect" indication balloon on top of it!
This way, by not seeing it, most of the time we forget to collect it and we lose valuable Scaryhearts.
The bug occurs on both platforms, iOS and Android.
EDIT: The same problem occurs on Crawlcrop statue too. For this reason I have updated the title of the topic.