title: Cowplot made ggplot2 theme disappear / How to see current ggplot2 theme, and restore the default?
body: <p>I recently installed the <code>cowplot</code> package. However, after doing this I noticed that my ggplots are missing their background and grid lines of <code>theme_grey()</code>!</p>
  
  <p><a href="https://i.stack.imgur.com/sruQE.png" rel="noreferrer"><img src="https://i.stack.imgur.com/sruQE.png" alt="enter image description here"></a></p>
  
  <p>The code to create each of the above plots is:</p>
  
  <pre><code>result_df %&gt;%
      ggplot(aes_string(x = 'p', y = 'r')) +
      # theme_grey() + # uncomment this line to produce plot on right
      geom_point(aes(group = c), size = 0.5) +
      geom_line(aes(group = c), size = 0.2, linetype = 'dotted') +
      theme(axis.text.x=element_text(angle = 90, hjust = 1, vjust = 0.5)) +
      facet_grid(b ~ e, scales = "free_y") +
      scale_x_continuous(breaks = seq(0, 10, 2))
  </code></pre>
  
  <p>Without explicitly calling <code>+ theme_grey()</code>, I get the plot on the left.</p>
  
  <p>What is happening here? I thought that <code>theme_grey()</code> is the default. How do I see what my default theme is?</p>
  
  <p>here is a snippet of my <code>sessionInfo()</code>:</p>
  
  <pre><code>R version 3.3.2 (2016-10-31)
  Platform: x86_64-w64-mingw32/x64 (64-bit)
  
  attached base packages:
  [1] stats     graphics  grDevices utils     datasets  methods   base     
  
  other attached packages:
   [1] ggthemes_3.3.0    cowplot_0.7.0     RPostgreSQL_0.4-1 DBI_0.5-1         knitr_1.15.1      dirmult_0.1.3-4   dplyr_0.5.0      
   [8] purrr_0.2.2       readr_1.0.0       tidyr_0.6.0       tibble_1.2        ggplot2_2.2.0     tidyverse_1.0.0  
  
  loaded via a namespace (and not attached):
   [1] Rcpp_0.12.8      magrittr_1.5     munsell_0.4.3    colorspace_1.3-1 R6_2.2.0         stringr_1.1.0    plyr_1.8.4       tools_3.3.2     
   [9] grid_3.3.2       gtable_0.2.0     lazyeval_0.2.0   assertthat_0.1   crayon_1.3.2     reshape2_1.4.2   rsconnect_0.6    testthat_1.0.2  
  [17] labeling_0.3     stringi_1.1.2    scales_0.4.1    
  </code></pre>