Originally Posted by
Quertus
Using that garden key is not optimal if
a) the garden is watched -> they are a1) more likely to be noticed and the guards of the room be on alert, or a2) likely to be noticed and the home invasion tied back to them after the fact;
b) the use of the fake rock / key is likely to be noticed after the fact, revealing that those who performed the home invasion (ie, the party) had that information, if their ability to have that information (psychic powers, informant, whatever) is something the PCs don't want getting out;
c) they want to frame some other group, whose modus operandi involves one of those other techniques;
etc.
What is a railroad is if you do not allow all the "kick the door down, pick the lock, search for a key, teleport, turn incorporal, shrink down and crawl under the crack, try and bluff someone into letting them in, create a diversion and force the guards inside to come out, tunnel through the wall, blow the wall down, dig under the wall, etc. etc. etc." solutions to work just because the rock and key exist / that's the solution you want them to use.