Short answer:
Yes
Explanation:
First, we have to bring this ruling from CRF, Turn Sequence Rulings:
However, this is the general rule for revealing on-guard cards, but Foolish Words has its own text allowing it to be revealed on-guard under certain circumstances:On-Guard Cards
Rules Erratum: An on-guard card may only be revealed if it could have also been played during the movement/hazard phase. This means all targets of the card must have existed during the movement/hazard phase in order for the card to be revealed.
If we only look at this CRF, it would seem that Foolish Words can’t be revealed on a character that wasn’t in play during the movement/hazard phase, because the target of the card didn’t exist.
This means Foolish Words follows its own mechanism of how it can be revealed from its on-guard state, which supercedes the general rule for on-guard cards from the CRF. Another example of cards that have their own mechanism would be Searching Eye; if it had to follow the general on-guard rule, it could never be revealed because the scout card it is canceling didn’t exist during the movement/hazard phase.Any riddling roll, offering attempt, or influence attempt by the target character is modified by 4. If placed on-guard, it may be revealed and played when a character in the company declares a riddling, offering, or influence attempt. During the organization phase, a character with this card may tap to attempt to remove it. Make a roll (or draw a #): if this result is greater than 7, discard this card. Cannot be duplicated.