I was thinking in terms of referring to a brain. Or, rather, a set of them. But a sufficiently detailed brainscan would work just as well, I suppose.

And, sure, the universe doesn't have a clock, but a clock isn't needed, simply an ordering: the AI attends to evidence about sensory experiences that occurred before the AI received the instruction.

Of course, maybe it is incapable of figuring out whether a given sensory experience occurred before it received the instruction... it's just not smart enough. Or maybe the universe is weirder than I imagine, such that the order in which two events occur is not something the AI and I can actually agree on... which is the same case as "perhaps it can in fact retroactively influence sensory experiences" above.