After getting off a Happy Ghast and leashing it to a fence post I walked away to do other things in the area but I never went very far away (never far away enough that even a non-tamed mob would despawn) and when i went back the leash had disappeared (not even dropped on the ground) and the ghast was gone, I looked around the area but it was not anywhere.
Thank you for your report!
We're tracking this issue in MCPE-221320, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support (Technical Issues) – 📧 Microsoft Support (Account Issues)
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki