How long is it safe to defrost frozen vacuum packed chicken in cold water
It sounds like you weren't using running water, which guarantees that the water the chicken would be sitting in stays at a constant temperature. Since you had left it in a standing pot of cold water, the temperature of that water probably got up to 50 or 60 degrees, depending on how cool you keep your house, which is most definitely within the danger-zone. Your chicken was not thawed safely. 

That does not necessarily mean that it was contaminated, but rather that it had the opportunity to become contaminated. 

Personally, I think you'll be fine, because your husband caught it before it was out for too long, but 4.5 hours is certainly pushing it. As long as you cook it properly to at least 165 degrees, the chances of you getting food poisoning are pretty slim.

Also, for future reference, if you are going to quick defrost chicken in water, you should only be doing so when you plan on immediately cooking it, rather than throwing it back in the fridge. See here.