I had a lot of issues getting it to appear correctly, I'm not sure if it's related to specific activity but it would appear like 1/7th of the time. Tbh you should just have it appear by default and remove itself once you've triggered dialogue. Or just have a dedicated button.
Viewing post in 2.0 is Out! ^^ Bug reports here please! comments
So after downloading the patch I think I figured out the issue. For whatever reason when the window resizes based on resolution it'll push the hearts UI outside of the frame. I tested by resizing the window and finally got the heart UI to appear correctly. I'd suggest seeing if you can set a default aspect ratio to force elements to appear correctly.