I am creating a gallery using AngularJS to talk to umbraco via the UmbracoApiController. My DocumentType has a String property and a MediaPicker property. I can't retrieve the MediaPicker property from the ContentCache. This is what I have tried:

public class ContentApiController : UmbracoApiController
{
    private static readonly ILog logger = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

    public object GetData(string url)
    {
        try
        {
            var content = !string.IsNullOrEmpty(urlName)
                ? UmbracoContext.Current.ContentCache.GetByXPath(string.Format(@"//*[@isDoc and @urlName=""{0}""]", url)).FirstOrDefault()
                : null;

            logger.DebugFormat("description exists: {0}", content.HasValue("description"));
            logger.DebugFormat("description value: {0}", content.GetPropertyValue<string>("description"));

            logger.DebugFormat("thumbnail exists: {0}", content.HasValue("thumbnail"));
            logger.DebugFormat("thumbnail value: {0}", content.GetPropertyValue<string>("thumbnail"));

my logs show: 2016-03-18 09:49:04,535 [54] DEBUG ContentApiController - description exists: True 2016-03-18 09:49:04,575 [54] DEBUG ContentApiController - description value: A superb .....

2016-03-18 09:49:04,575 [54] DEBUG ContentApiController - thumbnail exists: False 2016-03-18 09:49:04,576 [54] DEBUG ContentApiController - thumbnail value:

Is there another way to do this? I don't have the nodeId until I search for the content using the url.