annotation_owner_guid instead of owner_guid might be what you want.

You might also take care if using singular annotation_owner_guid or plural annotation_owner_guids. It's either

'annotation_owner_guid' => 45,

or

'annotation_owner_guids' => array(45),

When using owner_guid the singular / plural difference is the same. For all possible options of elgg_get_annotations or any other Elgg function you can check out http://reference.elgg.org.

Thanks iionly, I have missed the annotation_owner_guid parameter on the elgg reference website. I solved my problem.