[5000 linden missing from my account]

5000 linden is missing from my account 

looked in my account history   says I made a gift to  JeamsMcMastersSonoio  which I didn't.    this supposedly happened on july 28, 2013        I did not notice it till    today july 29, 2013

what can I do to get my lindens back?   I also looked at this persons profile,   The   born date for this person is   July 28, 2013

would you also email me an answer

Thanks

Susan