I had my bicycle seat and seat post stolen recently. Since I commute with my bike and couldn't ride it in its current condition, I brought the make and model information with me to Budget Bicycle Center. When I arrived, three separate employees told me I absolutely HAD to bring the bike in with me before they could order a seat post. When I asked if they could possibly look up the information (the bicycle was manufactured in 2014), I was told they could only look up that information for "higher-end" Schiwnns. The salesperson then told me that if I didn't get the correct seat post diameter, "bad things would happen". Ummm, I knew that seat post diameters varied BEFORE I walked in the store - any remotely observant person can figure that out! That is why I brought my bicycle information with me! I generally enjoy supporting local businesses, but this experience was just absolutely ridiculous.
A 5-minute phone call to Schwinn customer service was all I needed to get the seat post diameter information. Turns out the seat post was a pretty standard size - the first one I came across during Hippie Christmas fit my bike perfectly.