There is an object "Anchor Point" (type 3). It is automatically placed by the game near water, but apparently not when you remove objects via ERM. UN:O is really quite buggy, it doesn't even reset type/subtype.
As for getting all info. Let's say you do it, but then that tile may change in a way that you would want to keep (for example, some other objects getting into it from adjacent tiles). Then your saved state is useless, since it would revert all "good" changes.
I can write you some code that would simply save and restore raw tile data, but most likely it would make the game unstable or just crash it outright. Also saved data may remain valid just until game restart. Or until next game load.