Springs as in suspension springs? How the hell did that happen? Is it front or rear? Airbag or gas shock? More info...
Springs don't usually "wear out" and they are under a fair amount of compression even when they have no weight on them, so really shouldn't pop out - unless they have been cut or heated to lower the car, in which case they are ruined and junk, or if the rubber in the hats has perished it could perhaps cause an issue like this, though you would notice clunking and banging long before it jumped out.
I have no clue as to what other problems in an airbag strut could cause this, but again I would think its an indicator of terminal failure. If its happened once, it will happen again.
Springs are pretty cheap especially as you only need two of them. Should be able to get a pair for around $100 - $150 depending on brand etc. Fitting is easy especially the rears, and you already have the offer of a compressor. I just have a cheap set I bought from Supercheap for something like $40 and they work fine.