| Sounds like the old bolt has been "modified" to stop the original stand flicking up on it's own.
I wouldn't use it again. It can unscrew and let the "forked" part of the stand flex and ultimately break. Could be the casue of the failure.
Get the nut and correct plate for the spring and put it back as intended.
If you want to stop it flicking up, use the later nut and plate. | 
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