Lock's Quest

[ZanzibarGuy]

Hey all, hope this quest hasn't been posted before but I'm having trouble w/ Lock's quest. Specifically, I'd like to know where the whistle is, as I'm sure I need it to get beyond where I am. I've just finished level 5 and I've found a ton of secrets (including level 8) but I can't find levels 6 and 7 and I'm pretty sure I'll be needing the whistle to reach them.

Can anyone help me find either the whistle or at least another dungeon?