Answer

I think not. At most this is indirect causation, which, although one may still be liable in the heavenly sense, is not ordinarily collectible in court. And even that indirect causation here is not for the damage itself, but for expenses incurred by the decision of the purchaser, since he could have chosen not to make the celebration.
Perhaps one could compare this to showing a coin to a money-changer (an expert in coins), where if he misled the person, he is liable to compensate him. Here too there was, so to speak, the “testimony” of the scribe that the scroll was kosher. But this is a stretch, because the damage here is very indirect, unlike the case of the coin. The reasoning there is that he should have known better and did not. But in our case it would seem to depend on the type of mistake the scribe made and whether it was reasonable or not.

However, in a responsum of the Rema, section 12, he does obligate someone to pay a person who incurred expenses based on his word, but there he is speaking only where the expenses were necessary expenses, such as travel expenses to go litigate in another place. Here these were not necessary expenses, so at most it would be indirect causation.

Afterward I saw that apparently Maimonides and the Raavad dispute this in Hilkhot Zekhiyah U-Matanah 6:24:

“My teachers ruled that if it was the local custom for everyone to make a feast and feed his friends, or to distribute money to the attendants and cantors and the like, and he did as everyone normally does, and she then backed out, she must pay for everything, because she caused him to lose money; and anyone who causes another to lose money must pay. This is provided he has witnesses to how much he spent, for this is not a case where one swears and collects.”

The Raavad comments:
“I do not agree with his teachers on this. This kind of causation is similar to garden seeds that were planted and did not sprout, where he does not pay the expenses. The principle is that whenever the loss of money is brought about by the owner of the money himself, even though the other person caused it, he is exempt.”

And in the Shulchan Arukh, Even HaEzer section 50, subsection 3, the ruling follows Maimonides. The Chelkat Mechokek there writes that this is under the law of direct tortious causation.

However, there the case is one of intentionally canceling a wedding, whereas here this was unintentional. And the halakhic decisors disagree about liability for direct tortious causation when done unintentionally (see Shakh, section 386, subsection 4).

And in the case of showing a coin to a money-changer, they do impose liability, meaning that a mistake by an expert obligates him to compensate the person who acted on his word, because he should have known better and did not. Still,

Bottom line: it is difficult to impose liability as a matter of law, but perhaps there is reason to pay in the heavenly sense.
You can see the discussion in a court ruling here: https://www.daat.ac.il/daat/psk/psk.asp?id=2235