You used up the life in that bearing then.
More likely, it was "murdered" by the last person that worked on that bearing. They probably over-tightened the bearing to seat it, and then forgot, or didn't know about loosening it, then tightening it again, and backing off on the nut till the cotter pin easily entered the hole in the hole in the spindle. I have seen bearings fail, and most times, it was as a result of improper installation, and / or not being properly packed with grease. Front wheel bearings should be checked for looseness every 5000 miles, and checked and / or replaced if looseness is found. Once a bearing is overheated, it will self destruct quickly. Excessive over-tightening can damage the cage and / or the chrome plating on the bearings themselves. Also a visual inspection of the bearing, cage, and bearing race for damage, hot spots, and roughness. If any defect is found, replace both bearing and race as a unit. If you are not certain if the bearing is properly seated, then just tighten enough that the wrench shows some resistance, then loosen, spin the wheel, and retighten again and loosened enough to get the cotter pin into the hole. Spin the wheel and check to see if there is any resistance to spinning. Then check by lightly pushing on the wheel at 3 and then 9 o'clock to check for movement. It could have some slight movement, but will not be excessive if the bearing is properly set. If the wheel doesn't spin easily, and continue spinning after you take your hands off of it, the bearing is too tight or the bearing is defective in some way.
Bearings should be cleaned in solvent, then blown dry with compressed air, but never spun when dry using compressed air. Packing bearings is easy, but a little messy, and does take time to make sure that you have grease fully packed between the bearings and the cage. Improper bearing packing, or using the wrong type of grease will also lead to bearing failure.
https://www.youtube.com/watch?v=iGprSqnEh2A
While you are checking the bearing, place a large screwdriver or pry-bar under the tire at 6 o'clock, and lift. There should be very little movement in the upper and lower ball joints. Have someone observe where the movement is, if you find any. Also, to check the tie rods, once again try moving the wheel right and left at 3 and 9 o'clock and if you feel movement or clunking have someone observe the tie rods for wear while you move the tire/wheel.
https://www.youtube.com/watch?v=6M2D_XtuXZQ
One final thing is if you find a bad tie rod, and there is rust in the sleeve that connects the inner and outer tie rod, I suggest that you also replace the sleeve at the same time. If you find only one tie rod end worn, then consider replacing both inner, outer, and sleeve, since they are all probably the same age and mileage. You will need a front end alignment, and in the final analysis you will be saving money, since the labor and alignment will need to be done again, if the one that you don't replace fails a year or two from now. Worn steering parts if they fail can lead to disastrous results.