So we know that the Fidelius charm was cast to protect the Potter's location. I think in the third book it is mentioned somewhere that the location was hidden not the Potter's themselves. And I guess this would make sense as, as soon as you demonstrate what the Fidelius charm should hide it becomes useless. Therefore the Potter's would be restricted to stay hidden and every time they do something, which is typical for them the charm would be lifted. So I guess it is easier and much safer to just enchant their home like they presumably did.
And we know that only Peter knew about this location and told Tom about it. I guess in order to keep the attack a secret neither Peter nor Tom told anyone else so the Fidelius charm still remained intact even though more people knew about it. Therefore, when Tom entered the building and killed this should not have lifted the charm. Why would it? One of three was still alive. And I don't believe someone in Hogwarts or in the Order of Phoenix could have felt their death somehow as this protective spell should render all ways of finding whatever is hidden useless.
Still, shortly after the incident Hagrid, Snape, and Sirius appeared out of nowhere and immediately knew that this was the house the Potter's lived in...which should not work. I guess they were not the only ones who knew where their house was. If you could still remember that after the Fidelius had been used it wouldn't have been protective at all. And just because there was an explosion somewhere you wouldn't lift that super important protection just to check whether they are alright. I guess if this was the time where Voldemort was at full power cases like that happened every week.
So how could they remember their location and find them so shortly after their death?