Missing chest in the game??

[Zobeco]

I'm doing a 100% run and, i collected every other chest. (got a List from a site) there must be a purple chest in Grandport inside a guarded house and in grandport is only one guarded house in the middle with a grandma in it but no chest??

I searched in serveral sites in internet and every site have a purple chest in Grandport but i can't find it ?

I hope i don't have a bug

[Melodia]

Guides are wrong for some reason, it's actually in Marsalim.