It's very difficult for the untrained eye to determine height, including for instance cloud cover etc.
And the trained eye, too. Without measuring instruments it really is very difficult to estimate the height of an aircraft. On more than one occasion I've flown over my house and had people on the ground assure me that I was 50 feet above them. Really, they knew for sure, just about tree-top height.
And I knew for sure I was 1000 feet above them. I was reading from a reliable altimeter with correct pressure setting.
I'm not saying the OP is wrong (how could I? I wasn't there). However, planes above one in the sky frequently seem lower than they are.