After thinking about the ethics of the situation. I don't think there is any entitlement until intent has been declared. Arrival order is a poor indicator as it only indicates intent to purchase, not intent to occupy a table. How do you know that anyone in line is planning to sit at all until they declare such? Leaving some kind of object at the table to declare intent to occupy seems reasonable.

My friend suggested "the alternative would be no token-leaving allowed at all, the benefit of that being efficiency increase (higher table turnover rate) at the expense of predictability (as the person in line suffered from in this case)"