think i bought a stolen phone, how do I contact the owner

You don’t. You try finding the seller for remediation or refund, maybe hand it to the police, or you recycle it.

Apple is just not going to provide contact info for the holder of an Activation Lock.

Why not? Because some will find or steal a phone, then use that contact info to find more to steal, or worse.

The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community

According to The All Too Common SAD Reality of Buying a Used iPad/iPhone:

1. ONLY Buy Apple devices from trusted sources - An Apple Store or an Apple Authorized Reseller
2. If you can't afford a brand new iPad/iPhone, Apple and many Authorized Reseller's sell refurbished devices at reduced cost. These devices are often indistinguishable from a brand new device and they come with warranties.
3. Save your money and wait for a major holiday sale, where new devices are often discounted.
4. Don't become a victim. You worked hard for your money. Don't take the chance of being ripped off as so many are every single day.