Bucculatrix Cocoon?

[JulianB]

Found the following under the flaky bark of a veteran sycamore tree. The cocoon - if it is a moth cocoon (I first thought it was just a seed) was stuck tightly to the bark. It appears to have an exit hole. And it does have a ribbed appearance, similar to a Bucculatrix cocoon, although there's more swirling in the pattern. Bucculatrix thoracella seems to prefer lime. Might it be another Bucculatric species, or something else altogether?

Cheers, Julian