I noticed that the auto-suggest list disappears if a user clicks on a photo or GIF to enlarge it. When you come back the the chat conversation, the list is gone. You can pull it back up by clicking in the text area and pressing backspace, but this may not be intuitive to users. I have a feeling it will cause users to close out of the bot since they do not know what their choices are or how to see them. Explaining it in text may work, but it will no doubt break the experience.
This looks like a design issue. Will check it out and will come up with a design fix for this.
Thanks for noticing and reporting this