On the day of Pentecost the believers were in their home country. They did not learn a new language in one day as you prescribe. Please also point out where ever one that day were "missionaries" I can not find that in my bible.
PLEASE read the post carefully. I never said anything about them learning a new language at Pentecost, nor did I say anything about them being missionaries (though the apostles were somewhat missionaries after the Jesus ascended). I said that I believe another way that the gift of tongues is manifest is sometimes when missionaries learn another language. At Pentecost, the gift of tongues was used as a tool to manifest the power of God.