Chu Yu had not brought out the token given by Rong Zhi but had concocted a lie instead.
She falsely claimed that Rong Zhi was trapped by horse thieves and that she was entrusted by Rong Zhi to seek his help, hoping that Canghai Guest would lend a hand to rescue him.
The statement was half true and half false, the part about Rong Zhi being trapped being true, while the part about her being sent to seek help being false.
Chu Yu had thought of this lie on her way here, but at that time she couldn't be sure of who Canghai Guest was, hence she hadn't made any detailed plans. However, since Rong Zhi had willingly entrusted her with the important token, she presumed this person must be on Rong Zhi's side. If she asked for help in the name of Rong Zhi, she figured he probably wouldn't refuse.