Changing 'keep messages' in settings on ipad changed on my iPhone too!!!

i have an 128gb iphone and a 32gb ipad. I would like to have the ipad store messages up to 30 days old and my iphone store them forever. I also have messages turn on in 'icloud' on both devices, so that messages sync seamlessly across devices. e.g. if i delete a single message it deletes on another.

I recently read a post that this was possible as each device pulls data independently from eachother (although from the same source) so this would not be an issue. When changing this setting on my ipad however, i was prompted that messages older than 30 days will be deleted from 'your device' (note it did NOT say from ALL your devices). I proceeded and noticed that this setting has automatically been changed on my iphone too. I quickly changed this back to 'forever' on my iphone and the setting was mirrored back on my ipad again. All the messages have been deleted on my ipad now.

Please tell me i have not lost any of my messages.

In my mind, if the messages are synced to and 'live' encrypted on icloud, inst it just a simple case of asking each device to sync and store a different amount of data?

Surely this is simple enough to do! this would also be helpful for other data like photos etc.

Apple please help..