Comment by caminante

> Come Friday, no message [...] tanked my motivation to continue

I see the bookends, but notice the root cause

> That really kicked me into gear [...] I was very motivated and productive

You don't have intrinsic motivation for these tasks and the job. This is the thread to pull on. Keep asking "why?"

In the least, I recommend a pro-active note, letting him know you're done and ready for his feedback on the assignment or new priorities. Figure out why he didn't (or persistently doesn't) follow-up.