Pretty much the same thing happened to me. I got the Top Rated badge and I thought it would come with benefits, more exposure and whatnot. I also tried the promoted gigs feature like you did and since then less and less new people come to message me. I used to get daily messages, now it can be days without one. And when they come, many ask for services I don't even provide.
My response rate, delivery on time, order completion are almost always 100%. I have finished 1700+ orders and have an average of 5 star rating but for some reason I'm getting less and less noticed. I checked other similar gigs (in terms of service, rating, price, and completed orders) and they have numerous "orders in queue" so what happened to my gig? I know I can even provide better service than many of them.
So is using the promoted gigs feature somehow messes up the algorithm or something like if you stop using it your gig just gets tossed away to the 20th search page?