I agree with @Gnosego that the GM doesn’t have to give any intent a chance of success—no matter how slender. The rules on Wises even specifically limit a player’s ability to define new facts about the setting, which tacitly means certain more practical intents are impossible to achieve (for example, if you can’t add dragons to the world, then attracting them using a tethered goat is impossible in that world too).
However, I think the way the impossibility is expressed can matter: Gnosego’s example of the letter shows that unexamined assumptions matter as everyone’s first thought is likely to be that of course you can’t ask a dead relative about a letter they wrote—but in a setting ruled by necromancer lords “I want to talk to my grandfather about the letter” would seem like an entirely possible intent.
So, where something is impossible because a player has had their character assume something incorrect, my first thought would be whether the character should know the right answer (whether necromantic conversations are or are not possible) and if not, whether the confusion drives things in an interesting direction or dead-ends things. If all the confusion does is dead-end something, then just tell the player that their character knows/realises they were mistaken without needing a test. If the confusion can make things interesting, then make the test about whether the character remembers/realises the truth and then let them lean into knowing the right answer or actively playing their character’s misinterpretation.
In your example it sounds like end intent is serve the spirit, not speak to the spirit now, so the confusion over whether the spirit is there could be interesting. Tables are different, but I might have called for Spirits-wise (or some other suitable skill) to determine how you contact spirits, and then if the character succeeded told them their character realises this was only an echo of the past and those don’t tend to last longer than X hours and if they fail, tell them it was only an echo of the past but their character believes the spirit was there but didn’t find them interesting. That way, if they pass they know the spirits direction and that if they don’t follow soon the trail might fade, which creates a question of whether the group leave their current plan to help their colleague seek service with the spirit; and if they fail, it creates a BITs-worthy desire for the character to become someone the spirit is interested in (while making the player aware that they will also need to find the spirit).