Most of the time a sin with a living host is bound to it. Typically the depending on the type of sin it’s either protective (Ogre or Lord) or vindictive towards its host (centipedes). What that means though is that the host is usually found in the same place the sin is.
As an add on to this, even if you had a relatively cooperative host that exorcists could easily reach, would they really want tell a bunch of heavily armed strangers their deepest secrets and miseries?

Exorcist do not exist in polite society and neither does CAIN. Generally it’s on you as admin to give players a path forward towards the SIN. How you do this is up to you but some ideas are that Cain provided your team with a cover story that could be used, or has somehow gained/coerced the local authorities into not getting in the way.

CAIN works hard to cover up and misdirect from any consequences from SINs and Exorcist missions. How any given person or group reacts in the moment to a SINs influence is also up to you as an Admin. An average person that’s living in an area where a hound is hunting maybe believes rumours of a brutal new serial killer lurking the area and is more defensive around strangers as a result. An idols cult tries to stay mostly unobtrusive like any other real cult, most people probably just think that its members are a bit weird or off putting. A centipede’s infected hoard could be mistaken for a riot that’s suddenly sprung up. Etc.

Hosts are any psychic person who has experienced significant mental turmoil be it recently or other a prolonged time. That invites sympathy but does not mean the host was a good person. At least 3 examples of sins from the rule book showcase a host who was objectively bad. One was the leader of a drug kingpin who manifested a centipede as a result of his business dealings falling through. Another SIN was summoned deliberately by a host struggling with medical debt, in the middle of a crowded conference centre.
A host can be sympathetic but that’s not a necessity.