I’d send an email asking about a follow up. “This is FairyChatMom following up about the proposal for 123 ABC Lane. I was expecting a proposal by [date] and have not received it, do you have pricing prepared?”
Contrary to many of the posts here, I wouldn’t see getting a late quote out as indicative of the level of actual landscape service. More likely, they’re prioritizing actual contracts in hand and making sure those people are happy before spending time on potential new work especially if the sign up rate is fairly low (lots of free estimates, lots of sticker shock). Either they’re a smaller operation with one guy doing sales, estimating and project management or they could be a larger operation where they have a separate estimator who is overloaded but that’s not reflective on the production people.
Of course this doesn’t mean giving them infinite time and chances and, if you want to move on, move on. Just a different perspective from somewhat inside the industry (I’m in large commercial landscape installation, not small residential maintenance) and having been on both sides of the “Where’s my number?” question while getting vendor/subcontractor pricing.