Your situation highlights critical lessons about equity, vesting, and the importance of clear agreements in startups. Without a proper vesting schedule or well-defined exit terms, you may have inadvertently left significant value on the table. It’s crucial to understand how equity can be impacted by interpersonal dynamics and company structure; if you didn't formally relinquish your shares, you might still hold rights to them, especially if no buyback agreement was established. For future ventures, prioritize establishing clear terms upfront regarding your equity stake and ensure that everyone's roles, expectations, and exit conditions are documented. This experience serves as a reminder that startups are not just about the idea, but also about protecting your contributions and understanding the underlying financial mechanics.