I don't feel this thread is very clear and I think I can see why. The issue is to do with the core difference between the past simple and past perfect. Or rather, the mental events that would determine a speaker's choice of one aspect over another.
I think that the distracting element here may be the preceding I thought and when this thought happened.
In the examples of the boss and theatre-goer, the utterance I thought you left is perfectly understandable as the speakers are realising at that moment that the person didn't leave, so there's no need for a perfect tense. There's no retrospection from a point in past time. The I thought is distracting because they really mean I'm realising now that you didn't leave.
However, when I thought really does refer to a past thought, it would be likely that the speaker would use the perfect aspect, as in:
I sat in your seat because I thought you'd left.
Please let me know if that's not clear.
Hello jutfrank. I just want to let you know what I understand so far. First of all, I want to make it clear that I understand
this use of past simple after the
I thought as in the examples: I thought you forgot appointments. I thought you ate fish on Fridays. (provided by Roman55) which imply a habitual thing.
Now that I've got that out of the way, I would like to focus on the situations when I'm talking to a person in front of me in the present time, I say:
I thought we
moved/had moved past this. ( when you think you've already gone over a subject but your friend brings it up again)
I thought you
left/had left. ( you think the person has left but later you see him again)
I thought I
lost/had lost it. ( you think you've lost your handbag etc. but then find it)
I thought I
turned/had turned it off. ( then your cellphone rings)
I think that in all of the examples above logically past perfect should be used and the reason is that this is effectively
reported speech about an action in the past and we need backshift. But, we could also use past simple in all of them, and I have your post to back me up on this, since I'm saying that from a present perspective and the sequence is understood, so there's no need for past perfect.
Now I need you to tell me if I'm right or wrong.
Thanks.