Theme brake on teaser display

Hi.
I tried to implement hover preview but I have problem to implement it in teaser display.

If I try to call theme in full node display

print theme('hover_preview', $node, 'field_mycckfieldname', 'Thumbnail', 'BigImage');

everything appear as expected, but if I call it in teaser display there is nothing but link to generic image file.

Any idea what could make this issue?