[Okay Lucy probably should have thought this plan through better, because hey it's a little hard to write or do magic or, you know, function with one hand crushed into a fine paste, but right now Erza needs a little contact so she will shoulder through her fingers being placed in a vice for the moment with minimal wincing.]

I don't think it was a mistake. Maybe it doesn't feel right now, but if anyone else arrives, then all they'll have to do is see this place, and they'll know their Nakama is waiting for them.