Ok..how does this happen?

^Some bolt manufacturers produce recommended torque tables. For example this is from Fastenal: http://www.fastenal.com/content/feds/pdf/Torque-Tension Chart for A307 Gr5 Gr8 Gr9.pdf

 

Glad to hear you were able to fix it.

I also agree with the opinion that whoever installed the suspension probably forgot to torque that bolt. As somebody said in a post above, it happens more often than what people realize. In addition to loose bolts left by techs, over the years I've also found a couple of ratchets and good assortment of sockets left in various places of my engine compartment

 

I work in Production Maintenance at a huge Honeywell plant, can't tell you how often I find my "lost" tools when I get back to a piece of equipment I did PM on 3 months ago. Bolts or nuts left loose is bad news, yet it still happens, usually when in a hurry or if getting interrupted. That is why I put my Icon suspension on myself with the help of a buddy.

Suspension hardware needs to be secure and checked afterward as suggested.

 

hahaha, glad to hear you found your tools. Better late than never

Working on tacoma suspensions is quite simple. Anybody with basic mechanical skills can do it for sure. But at times convenience is more important, so I understand why some people have their suspension installed at a shop.