Screaming or howling in Boone County, Missouri

I am 27 years old now, this happened when I was about 11, I believe the year 2000. I realize I was young, however, I have thought about this experience many times over the years and have not been able to explain what was seen that day. I was with two other people, one female who was my age at the time and her brother who was about 13-14 years old. The two of us girls were walking and he was on a bike. We were on the outskirts of Columbia, MO, I am not sure of the exact location but I did force my dad to walk that path with me again in the days after so I'm sure he would remember. The bike path was wooded on both sides, the weather that day was overcast but since it was the middle of the afternoon the visibility was fine. We were about 30 yards from where the path opened up to a lake. We were just walking and chatting and, unannounced, this creature walked out of the left side of the woods (no excessive noise, just a little bit if rustling like a deer was moving around) it then crossed the path and moved up into the right side of the woods. No drama, no growling or screaming... it did nothing to spook us. It just quietly and matter of factly walked from one side of the woods to the other. It did not look at us or do anything threatening. It was only about 6-6.5 ft tall, fairly thin (lanky almost.. the best way to describe it I find is to compare it to an Irish wolfhound dog on two legs, without the dog shaped facial structure). It had longer, stringy hair. The most striking part to me and what I remember most clearly, is that it's hair was grey, not brown. It was a dirty-grey type color. I did not see any facial features distinctly. It's gate was long-strided, the arms were longer and I remember they swung by its sides in an ape-like manner. The entire encounter was fairly short and unassuming. We saw this creature walk calmly across the path, no one said a word but we all wheeled around and ran the entire way back to the house.. I just remember being genuinely scared. I know I was young but I know I saw something that I struggle to comprehend or explain even today. I don't know if Bigfoot is a real animal but I know what I saw was not just someone trying to scare us.