When looking at the rules and following them strictly, I would say you don't have to make a Hide check.
Black Riders Rulebook p. 7 wrote:
Hide X is a new keyword in this scenario. When an
encounter card with the Hide X keyword is revealed, the
player who revealed the card must make a Hide test. If
the encounter card with the Hide X keyword also has a
“When Revealed” or “Forced” effect, the Hide test must be
resolved before resolving the rest of the card.
(1.22) “When Revealed” Effects
A card is only considered to be revealed if the card or
game effect causing the card to enter play specifically
uses a form of the word “reveal”.
Example: If the players use the Stage 3b “Don’t Leave
the Path!” (CORE 121) quest card effect to search
for a King Spider and put it into play, the “When
Revealed” effect on the King Spider will not trigger,
since the effect on “Don’t Leave the Path!” does not
specifically use a form of the word “reveal.”
Piercing Cry does not use any form of the word reveal in its text. Therefore it seems that the Hide efect does not trigger.
I know in this game it often feels unlikely that there happens something to the advantage of the player , but this is at least how I read the rules.