BindingSource IndexOf question

I have having difficulty using the IndexOf method of a BindingSource
object. I am able to find the correct row by using "
this.isvgDevelopmentDataSet.individualTBL.FindByindividualID
(individualID)", and this binding source is set up for the
individualTBL, BUT the IndexOf method keeps returning -1 for not
finding the row object.

....

individualID = id;


int pos = this.individualTBLBindingSource.IndexOf(
this.isvgDevelopmentDataSet.individualTBL.FindByindividualID
(individualID));

this.individualTBLBindingSource.Position = pos; //doesn't work, pos =
-1

.....

Any ideas why this is so?