"I thought you had left us" vs "I thought you would have left us"

What is the difference between these two sentences: "I thought you had left us" vs "I thought you would have left us" I believe there is a distinction, namely whether you did in fact leave or not. In that case, there are two options regarding this sentence, namely:

1) "I thought you ...left us, but you didn't!"
2) "I thought you ...left us and we were right!"

If this distinction is in fact true, which sentence would you use for which situation?

"I thought you had left us"

is usually used as a simple counter-factual statement that sets up a contrary proposition ("... but I was wrong," etc.).

"I thought you would have left us"

is a more complex creature. It still suggests that "you" did not leave, but the use of would have implies an expectation on the part of the speaker that "you" may have had had some reason to leave—a plane to catch, an illness, an affront to your dignity, whatever—but you chose to stay in spite of that.