Controller and visualforce page to demonstrate missing records with UserRecordAccess query.

UserRecordAccessDebug.page

<apex:page controller="UserRecordAccessDebugCtrl" showHeader="true" sidebar="true">
  <!-- 
    Load this page with a record in the 'id parameter as users with varying record access
  -->
  <apex:form>
    <h2>User</h2>
    <br />
    <apex:selectList value="{!userId}" size="1">
      <apex:selectOptions value="{!userOptions}" />
      <apex:actionSupport event="onchange" rerender="debug" />
    </apex:selectList>
  </apex:form>
  <br />
  <apex:outputPanel id="debug">
    <h2>Access</h2>
    <p>{!accessDebug}</p>
    <h2>Record</h2>
    <p>{!recordDebug}</p>
  </apex:outputPanel>
</apex:page>

UserRecordAccessDebugCtrl.cls

public without sharing class UserRecordAccessDebugCtrl {

  private Id recordId {get;set;}
  public Id userId {get;set;}
  public List<SelectOption> userOptions {get;set;}

  public UserRecordAccessDebugCtrl() {
		recordId = ApexPages.currentPage().getParameters().get('id');
    userOptions = new List<SelectOption>();
    for(User u : [SELECT Name, Username, Profile.Name FROM User ORDER BY Name]) {
      userOptions.add(new SelectOption(u.Id, u.Name + ' [' + Profile.Name + ']'));
    }
    userId = userInfo.getUserId();
	}

  public String getAccessDebug() {
    return JSON.serialize(Database.query('SELECT RecordId, MaxAccessLevel FROM UserRecordAccess WHERE RecordId = :recordId AND UserId = :userId'));
  }
  
  public String getRecordDebug() {
    return JSON.serialize(Database.query('SELECT Name, UserRecordAccess.HasEditAccess FROM Opportunity WHERE Id = :recordId'));
  }
}