Phone deleting imessages

Smart Phones neither have the intelligence nor has the hostility. Hence we need to look at our device settings and the way we synchronise our smart phones with Mac/PC/iCloud and also how careful are we in sharing our sensitive and valuable information with friends and family members.

Be careful when sharing the device's sensitive and valuable information with friends and family members.

Thumb Rules:

1. Enable  Guided Access before handing over an iPhone to kids
2. Don't share Apple IDs
3. Don't Jail Break
4. Don't share sensitive information pertaining to your device and payment methods
5. Is this your corporate iPhone? Do you have any profile installed by your corporate / organisation / enterprise / School Management? Then please contact the system administrator of your corporate / organisation / enterprise / School Management. If you have installed it on your own --> Install or remove configuration profiles on iPhone - Apple ...

a lot of weird issues can be with icloud try to sign in and out of both devices and if that doesnt work see if your imessages are saved to your phone backup that could be an issue. (havent had experience with this so just guessing)