This is our dissent. I say that it is "attachment" (or "clinging") that can be directly experienced but you prefer "thinking about" and infer "it must be existence that is 'felt' and that causes the clinging". I consider this to be philosophical fabrication deviating from direct experience and leading to further deviating fabrications and ... to "the thicket of views".
You seem to be clinging tightly to a thicket of views in an attempt to avoid that thicket.
"It exists", "it does not exist" is an ingrained habitual imputation -- that is a view,that is also a thought. Apart from these two views, there are no other views since all views can be summarized into these two positions or thoughts.
The ingrained habitual imputation "It exists" or "it does not exist" is the cause of clinging or attachment. There is no existence to be "felt". Existence/non-existence is an imputation that lacks a basis.
From another perspective, clinging can never be an unmediated experience since it is following craving, which follow sensation. When there is no craving, there can be no clinging. When there is craving, this is accompanied by the thought, "I want this", "I don't want that".
A sensation on the other hand, does not necessarily involve clinging since sense consciousnesses are wholly non-conceptual, and and their object is in the present moment. Clinging is an operation of the manas, and therefore, constantly involved with past moments of sense perception. Hence clinging is a wholly conceptual state, divorced from non-conceptual sense cognitions, based on craving. Craving is also function of manas, and is also supported on a past object, the object of sensation produced during contact.
So, while it is possible to experience an attachment directly that experience is based on a thought, divorced from the sense percept of that object of attachments. Attachment therefore, cannot be direct experiences, although they themselves can be directly experiences as mental objects.