Help needed with Regular Expression search and special characters

Elastic Stack Elasticsearch
1

I'm trying to do a regex field on a not_analyzed field that contain text that conform to the following:

word word keyOne=(20),keyTwo=(30)

I've tried various permutations to get a regexp query working to find documents with two or more numbers inside the round brackets after keyOne:

{
  "query": {
    "regexp": {
      "message_raw": "keyOne=\\([0-9]{2,}\\)"
    },
    "analyzer": "simple"
  }
}

This does not match:

{
  "_index" : "test",
  "_type" : "messages",
  "_id" : "AVUQAVW63lfkFHq9cox-",
  "matched" : false,
  "explanation" : {
    "value" : 0.0,
    "description" : "Failure to meet condition(s) of required/prohibited clause(s)",
    "details" : [ {
      "value" : 0.0,
      "description" : "no match on required clause (message_raw:/keyOne=\\([0-9]{2,}\\)/)",
      "details" : [ {
        "value" : 0.0,
        "description" : "message_raw:/keyOne=\\([0-9]{2,}\\)/ doesn't match id 0",
        "details" : [ ]
      } ]
    }, {
      "value" : 0.0,
      "description" : "match on required clause, product of:",
      "details" : [ {
        "value" : 0.0,
        "description" : "# clause",
        "details" : [ ]
      }, {
        "value" : 1.0,
        "description" : "_type:messages, product of:",
        "details" : [ {
          "value" : 1.0,
          "description" : "boost",
          "details" : [ ]
        }, {
          "value" : 1.0,
          "description" : "queryNorm",
          "details" : [ ]
        } ]
      } ]
    } ]
  }
}

The only match I could get, was the following:

{
  "query": {
    "regexp": {
      "message_raw": "[0-9]{2,}"
    },
    "analyzer": "simple"
  }
}

And the explanation:

{
  "_index" : "test",
  "_type" : "messages",
  "_id" : "AVUQAVW63lfkFHq9cox-",
  "matched" : true,
  "explanation" : {
    "value" : 1.0,
    "description" : "sum of:",
    "details" : [ {
      "value" : 1.0,
      "description" : "message_raw:/[0-9]{2,}/, product of:",
      "details" : [ {
        "value" : 1.0,
        "description" : "boost",
        "details" : [ ]
      }, {
        "value" : 1.0,
        "description" : "queryNorm",
        "details" : [ ]
      } ]
    }, {
      "value" : 0.0,
      "description" : "match on required clause, product of:",
      "details" : [ {
        "value" : 0.0,
        "description" : "# clause",
        "details" : [ ]
      }, {
        "value" : 1.0,
        "description" : "_type:messages, product of:",
        "details" : [ {
          "value" : 1.0,
          "description" : "boost",
          "details" : [ ]
        }, {
          "value" : 1.0,
          "description" : "queryNorm",
          "details" : [ ]
        } ]
      } ]
    } ]
  }
}

I know it would be best to parse the message before sending it into Elasticsearch, but I'd still like to know why the regular expression doesn't work properly.

Any thoughts? Should I create an issue?