Hate to tell you this, but that wasn't smart on your part. Baker Beach is part of the GGNRA, and is patrolled by park rangers. Parking there isn't really stealthy. Not to be preachy, but I don't think overnight camping is allowed. Those guys should not have been there either. You're probably lucky they weren't there to cause trouble. I grew up in SF and I generally have a pretty good street sense.
Head across the bridge over to the more isolated parts of Marin towards Point Reyes if you want to stealth camp.
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