I'm married but when I take myself out it's definitely happened to me.
We live and work in a little place of only 3,048 so all the cafe's and the Fine Dine Indian restaurant around here know me and my hubby so they just serve me properly anyway, I/we're on first-name terms/friendly with them but when in an area when they don't know me, like you, it's like I'm invisible! But I've notice they'll serve single-seated MEN as normal!
If it's one of those places where you pay after the meal, I'll patiently wait for a reasonable amount of time but if I've still not been seen to or order or if my meal hasn't arrived in reasonable time then I just walk out then give them a VERY bad review on on their website or TripAdvisor!