<lightning:tabset>
<lightning:tab tab1>
<c:component_in_tab1 aura:id="tab1" />
</lightning:tab>
<lightning:tab tab2>
<c:component_in_tab2 aura:id="tab2" />
</lightning:tab>
</lightning:tabset>
var cmp = component.find('tab2'); // THIS THROWS UNDEFINED
var dataAttribute = cmp.get('v.myAttribute');
