The thing is, I had the best dream of the night after I had woken up and then gone back to sleep quite early in the morning. Is this what's often referred to as 'Wake Back to Bed' (WBTB)?
Yes, indeed it was a WBTB. Not sure about the supertechnical side of it, but basically when you wake up a few hours into sleep, you are still in REM, and so when you get back to sleep, everything seems much more vivid and memorable. This is why it is recommended to be paired with the other techniques, since you have better chances of getting lucid then.