stat_density_2d plot ignores fill aesthetic

Question

Below is R code (dataset included) that aims to replicate the style of this heatmap using a stat_desnity_2d plot.

The code runs, but the code is ignoring my fill variable (titled "exitspeed" in the code) therefore the plot is showing only one color. Below is a picture.

Does anyone know how to get a stat_density_2d plot to stop ignoring the fill variable (exitspeed) so that the output looks similar to the picture in the paragraph above? Thanks in advance!

Here is the dataset:

structure(list(platelocheight = c(2.594, 3.803, 3.254, 3.599, 
3.617, 3.297, 2.093, 3.611, 2.842, 3.316, 2.872, 3.228, 3.633, 
4.28, 3.309, 2.8, 2.632, 3.754, 2.207, 3.604, 3.443, 2.188, 3.452, 
2.553, 3.382, 3.067, 2.986, 2.785, 2.567, 3.804), platelocside = c(0.059, 
-1.596, -0.65, -0.782, -0.301, -0.104, 0.057, -0.807, 0.003, 
1.661, 0.088, -0.32, -1.115, -0.146, -0.364, -0.952, 0.254, 0.109, 
-0.671, -0.803, -0.212, -0.069, -0.09, -0.472, 0.434, 0.337, 
0.723, 0.508, -0.197, -0.635), exitspeed = c(69.891, 73.352, 
83.942, 85.67, 79.454, 85.277, 81.078, 73.573, 77.272, 59.263, 
97.343, 91.436, 76.264, 83.479, 47.576, 84.13, 60.475, 61.093, 
84.54, 69.959, 88.729, 88.019, 82.18, 83.684, 86.296, 90.605, 
79.945, 59.899, 62.522, 77.75)), .Names = c("platelocheight", 
"platelocside", "exitspeed"), row.names = c(NA, 30L), class = "data.frame")
> 

R Code:

library(RODBC)
library(ggplot2)


    con=odbcConnect('username',uid='ID', pwd = 'password')

    df=sqlQuery(con,"select platelocheight, platelocside, exitspeed from pitches_sample where pitchcall='InPlay' 
                and exitspeed is not null")

    topKzone <- 3.5
    botKzone <- 1.6
    inKzone <- -0.95
    outKzone <- 0.95
    kZone <- data.frame(
      x=c(inKzone, inKzone, outKzone, outKzone, inKzone),
      y=c(botKzone, topKzone, topKzone, botKzone, botKzone)
    )

    df$h <- round(df$platelocheight)
    df$s <- round(df$platelocside)
    df$es<- round(df$exitspeed)

    ggplot(kZone, aes(x,y)) +
      stat_density_2d(data=df, aes(x=s, y=h, fill=es),geom="polygon") +
      scale_fill_distiller(palette = "Spectral") +
      geom_path(lwd=1.5, col="black") +
      coord_fixed()