This simple little wanted poster-style message refers to the llamada perdida, or lost call. Not sure if this is something people do all over the world or just in Spain. If you want to let someone know you’ve arrived somewhere for example, you tell them that you’ll give them a “llamada perdida”. This means you’ll call them and let it ring just enough times for the person to read their caller ID,but they don’t pick it up. This way, you’ve sent your message without being charged for the call. I imagine this sign was left by a lonely soul who had been waiting a little too long for his lost call.