I do think, though, that Savvas and Amy were trying to get out a message(s) through their calls and texts, but could only do it in the most vague of ways so as not to the rouse suspicion of their captor(s). I especially feel that there was one moment when things could have gone a different way, and that was when Vera's husband came to the house on Thursday morning. I think he knew it was completely outside of the norm that his wife would have stayed over at the Savapolous' house on Wednesday night. She was a cleaner, though a housekeeping service, not a live-in housekeeper. Even if her husband was told that her phone wasn't charged, etc., he was probably still wondering what was going on, so much so that he came to the house to try to find her the next morning. I believe something did not feel right to him and he was, naturally, concerned for her welfare. Some part of him, probably, still felt like something did not feel right even when he spoke with Savvas, who told him that Vera was with Amy at the hospital but, and this is me just being speculative, I think it's hard to question what is being told to you by someone who is, ultimately, your wife's employer. What if his concern was misplaced, and she really was helping out the family and with Amy, and he called the police? Would the Savapolous' be angry with him for that, think he over-reacted, and his wife would lose her job? Perhaps he put all that concern and worry out of his mind, told himself that his wife was a nice person, trying to help out this family when they needed her, and that he was being silly and was sure she would call him when everything settled down. As said above, hindsight is 20/20 and I imagine the poor husband is just wracked with guilt for not having followed his gut and called the police.
While I don't think they were trying to get the message out, I completely agree with your take on VF's husband.