There is only one heartbroken imp (CG1)

Unfortunately you're probably right. Some time ago we fixed some of the issues with heartbroken imps not spawning in pairs, but the full solution continued to elude us right up until the final release of the game. (As you may know, the dev team has now moved on to work on the sequel.) Here is some advice on the topic:

• There will occasionally be two heartbroken imps, so please take advantage of those opportunities when they arise.
• Conversely, before trying to help a heartbroken imp please make sure that there are two of them
• Imp locations, and even which imps are/aren't there, don't persist across play sessions. So if you see two heartbroken imps, try to help them in that play session. Don't, for example, save the game thinking that you'll be able to come back later and help them—they may not be there when you load the save.
• Sometimes hungry and heartbroken imps incorrectly won't have a speech bubble over their heads.
  • If you see an imp crying, it's probably heartbroken even though it never asks for a bon bon. Try a bon bon anyway and see if it behaves like a heartbroken imp!
  • If you approach an imp and it doesn't run away, but also never displays the crying or bonbon animations, it's probably heartbroken. Try a bon bon anyway and see if it behaves like a heartbroken imp!
  • (If it does run away when you approach, it's probably either hungry or a normal imp.)
• Exiting and relaunching the game can sometimes help, but this should be your last resort because it may make one or both imps in the pair disappear rather than making the missing imp appear.
• If all else fails, don't worry about it today. The game takes many days to complete, and on at least some of them there should be a proper pair of heartbroken imps to help.