3 weeks is 21 days, which is about half the time you'd need to die of starvation, assuming no other nutrient intake (and no water insecurity; you'll die in only a few days without water, even dirty water). That's likely not really what happened in this guy's case, since - and I speak from experience here - when you get that desperate, you get remarkably resourceful. Old multivitamins that you forgot were in the back of the cupboard and have sat there for at least 3-4 years? Yep, eat 'em. That freezerburned leftover scalloped potatoes at the bottom/back of the freezer from last year? Yeah, not the tastiest thing but it sure beats nothing. Out of everything else? Go see people at Sam's Club or Costco, or anywhere they give out free samples. Even a small bite can sustain you for a remarkably long time, much longer than you might think. The human body is _incredibly_ efficient; as a culture, we in the US eat just way more than we need (most of us, that is, myself included); so what passes for a "meal" for most of us, in a starvation context, could keep you going for 2-3 days.
So no, I don't think he's making this up, nor do I think it's sarcasm. I've been there. And take my word for it, because I hope you never have to find out for yourself, but the worst part of that scenario - being homeless or near-homeless, having no food - isn't the hunger. It's the fear.
There is no soup kitchen here. There is one food bank, which is only open once a month for a couple of hours. I haven't been, so cannot say whether they attempt to provide a month's worth of food or not.
The last food bank I went to operated twice a week and attempted to provide a week's worth of calories in pre-sorted bags of goods. Recipients were limited to 2x/mo. Obtaining a larger bag (e.g. for a family) required providing official state-issued photo ID for any and all additional recipients, which was then logged and counted as part of each individual's 2x/mo limit.
I predict we'll see a lot more stories like these, and worse, coming out of the US in the coming months and years. Not nearly enough is being done to address the underlying problems, and it's got to be a problem of cataclysmic proportions before Congress will even consider a 5-minute discussion over lunch, let alone draft a bill with any real teeth (regardless of party).
But anyway, we know too little about OP to make assumptions about his economy