You did right telling an admin. The admin was right warning first, too. That's our policy here. You can't expect any admin interrupting his game immediately just because some player screams "blocker" or "destroyer". Do you know how oftne players abuse this, trying to troll admins? Can you imagine an admin is playing with anohter player, defending a spot against numerous enemies? Wouldnt it be unfair if the admin goes to spec, leaving his mate behind? Woulndt his mate beliefe that the admin is abusing his power to avoid death? I am sure you understand what I mean.
Still: This isnt a cade, it's a single sofa in a ridiculous spot. A sofa that can be pushed by E, a sofa that prevents players who want to hold this spot to shoot. A sofa that flies away if a player sprays bullets.
I understand it if players (like you) want to try out new ideas (I did myself), to me it's a big part of this game - but you cant expect all other players to stop shooting and defending their spot just because you had the idea of pushing a sofa into the shooting direction of a highspot. They want to camp there and deliver headshots to the enemy to score points. That's the original idea of the game (except for the camping part ofc^^).
How you should act in this case? Laugh about it, it didnt work, maybe next time. Sooner or later you'll be on a spot like this with another curious player who wants to test your idea. (Spoiler: it wont work like that). And in all other cases you'll be up with players who are playing to survive and to score - and they will shoot regardless of your sofa.
Hope you got me right this time.