Just learned about this species. Gall is laminal, not marginal like it usually is with T. coweni, and it is sort of a hollow scoop on the underside as you describe, not with an inner chamber.
icosahedron
2013-05-13
2013-05-13 1000
United States of America, California, Foothill Regional Park
Manzanita leaf lesions: red hemispheric distortions of many leaves on these hillside plants. Thought they might be galls of some sort; but they proved to be carmine 'bubbles' of the leaves...