If you were only a few days late on your period, and you were in fact pregnant, it would be called a chemical pregnancy (before the embryo has a chance to implant properly). It is very common, it's just that most women won't know it's happening. They just assume their period was a bit late that month. There's probably nothing you can do to avoid a pregnancy loss that early. It's usually caused by a "defect" in the embryo, like a chromosomal abnormality. It just happens sometimes...
I'm not sure about the tissue, though, because at this early stage, everything is so microscopic that I'm not really sure you would be able to "see" anything (if that makes sense).
I wish you all the best on your TTC journey and I hope you'll get another BFP really soon!
Take care!
Only a doctor can diagnose m/c but honestly that sounds like what it might have been. Cause of miscarriage could be many things: low progesterone, genetic abnormality caused by a defective egg or sperm, etc. You should be seeing your doctor for fertility care while you're TTC and you need to make sure you passed all the tissue. So call your doc tomorrow and make an appointment. I am so sorry for your loss, if that is what has happened.