This bug has appeared in more previous versions (even before 1.14 I think) and affects Android and possibly all platforms of Bedrock. If you have saved a structure via both Structure Block and /structure command, then place another structure block and type the name of said structure, it overwrites the saved structure with the currently selected area, even if you haven't pressed Save.

Steps to reproduce

1. I select my house and save it as a structure using a structure block with the name my_house.
2. Then I place another structure block on a patch of grass and type my_house in its prompt box, but with the Save mode still selected.
3. I switch the structure block to Load mode (or place another structure block, switch it to Load mode, and then type my_house in the box), and then click the Load button.

Expected result

The structure block loads the structure that was saved in step 1.

Actual result

The structure block loads the patch of grass that was selected in step 2, having overwritten the house that I built.