First Signal vs Clearblue sensitivity

Hey guys, so I took one of the 88 cent First Signal tests and I watched as the test developed (I know I'm bad, right), and I didn't see anything so I walked away. I came back within the 10 minute time frame and there was the faintest of lines. It wasn't a thin one like an evap, it was the same width as the control but it was just a vvvfl. 
The next morning I took a clearblue non digital with fmu just to see if anything would show up. I guess I am crazy because absolutely nothing came back on the clearblue. 😕 
Has this happened to anyone else before? Getting positives on first signals that weren't detected on other tests yet? Or am I just crazy? Side note, I didn't take any pics 😩