In-Table Foreign Keys in DataMapper ORM

[eluser]WanWizard[/eluser]
Datamapper has built-in support for ITFK's for one-to-one and one-to-many relations, it will detect and use them automatically.

Now, you're stating you're using an advanced relationship definition, which means you overrule the automatic detection because you define everything by hand.
Which is where the problem must be, but since you don't give us your schema (of the tables involved), nor the model definition, all I can do is guess.