Related narration is as follows:
As narrrated by Abu Hurairah, The Prophet (saws) said: ‘There are three things which, whether undertaken seriously or in jest, are treated as serious: Marriage, divorce and taking back a wife (after a divorce which is not final).’ (Abu-Dawood, Talaq, 9)
The meaning of the hadith is not that, divorce and marriage words in jest are taken seriously, but that a person cannot say it was in jest after an orderly performed divorce or marriage.
As for the question, calling each other husband and wife in public does not make a woman and man real husband and wife.
A valid marriage according to its requirements (such as witnesses, inspection of the wali of the woman) must be performed to be husband and wife. Please visit the following link for details of marriage: