After searching google and SO, I see that there is a way for me to search a dictionary for an existing key:
dict.exists(\"search string\")
If you want to use a wildcard to search in dictionary keys you can use the method [yourdictionary].Keys and the function Application.Match
For example: Dim position As Variant 'It will return the position for the first occurrence
position = Application.Match("*Gonzalez", phoneBook.Keys, 0)
If phoneBook has Keys: (JuanCarlos, LuisGonzalez, PedroGonzalez)
It will return the position for LuisGonzalez