If you use the back arrow, you are going back to the page Before you gave the flower, so you won't see one. Either click on the tab on the top, or the name at the top.
Usually that only happens when I use my back arrow. but even then, if I refresh my page the flowers are actually still there.
Ssometimes when I reply to a post and leave a flower then go back to original post the flower is not there so I just give another one. Not sure why this happens. Maybe we have a little gremlin at work. lol
Happens to me a lot. Just keep trying, should come up sooner or later. leaving you a flower..