Proof coins retain their value based on condition of the coin, not on the packaging so it just depends how they were handled, although modern proof coins may not hold much added value outside of a set but you can check on individual values at pcgs or ngc.
In late 2008 and into 2009, economic conditions slowed the movement of coins within circulation and caused Americans to cash in hoards of old change. During that time there was a bunch of proof and non proof coins alike that were put into circulation. Sometimes people just have modern proofs that are held for awhile, then dumped back in change as they realize there was no added value over what it would cost to grade, or perhaps get out of collecting or had trouble selling otherwise. Sometimes you might see colorized, hologram, or silver/gold plated coins for similar reasons where the person realizes its not an investment and for whatever reason doesn't want them for a collection anymore. And maybe as you mentioned due to the individual persons health, as their children or family might not want to deal with them and just put them back at the bank or even coinstar.