As we cannot read thoughts, how else might consciousness manifest if not by word or deed?

It's more of a framing thing, like 'failed to reject the null hypothesis' or 'not guilty' instead of 'accepted the null hypothesis' or 'innocent'.

Consciousness can exist independent of our ability, or even our possibility to recognize it. That doesn't mean things we can otherwise perceive necessarily lacks conscious. Also imo consciousness is a matter of magnitude, not a binary classification.

I get a lot of people will say 'well what's the relevance of a conscious entity that I cannot communicate with', and my response would be 'well communication or action may be unidirectional, in that we affect the conscious entity even if it cannot affect us'

This is another reason I want to be cremated. The case of my formerly conscious arrangement of grey matter is something this consciousness wants to scramble beyond repair when death or permacoma comes for me.