Hi, David! Looks like we're neighbors, relatively speaking.
Gladiolus blooms go off quickly like a firework, starting at the bottom. I don't think a single one lasts for 2 weeks @ my house. If you haven't visited the spot where they are almost weekly during their short bloom period, it's understandable that you would have missed them before if they were already big enough to have bloomed in previous years.
These are not unusual to spot in ditches along dirt roads in the area, or just randomly in a rarely mowed spot.
If you keep an eye on them, you should be able to collect seeds when they are ripe. They make a lot of seeds. Seed-grown bulbs would take a few years to reach mature, blooming size. As said, for other color options, often a mystery mix, you can buy bags/boxes of Gladiolus bulbs at Lowe's, WM, HD, but they are probably already gone for the year. If interested, look for them in Feb/March next year. Or you could probably find Gladiolus bulbs online if you wanted to pick a specific color.