After Trading Lost My Things

[WQZYLPRIME]

After i trade with people, for example i sell my riven, and other give me plat. After trade, buyer get my riven and his plat decrease. But for me, i dont have my riven, and my plat didnt increase. It happened at least 3 times in my memory. First time, several days, may be 2 or 3 days ago, i trade with my friend, i give him my unroll Paracesis riven, and he give me 350 plat. But after trading, my plat didnt increase. And this afternoon(for China , about 3pm, maybe), I sell my plague kripath riven, and a person give me 1200. My plat still didnt increase. Just now, i trade with my friend iD = "CHUNBIYUAN", still cant get what i want to trade. This time , i take a screenshot。When I click "确定", and check my mod(we are teading mods), i cant find  the mod he give to me. 

[WQZYLPRIME]

THIS for detail. 

My net is not so good, i have to wait 2 mins to see people who i want to trade. Receving trade request from him and Show my trade window alse need some time to wait. And when i put my riven or mod or other things, and then i click "准备交易"(or else, i forget the words )  i usually need to wait some time to be ready to click"接受交易"("accept trade" in english). And from many days ago, i find when i click and unclick  "准备交易"(or else) button, it show "接受交易"("accept trade" in english) button quickly. and i can click it  no need to  wait some time. But some time , it will say i cant trade with other,just like image that i show. And this days, i find when i have this problems, i cant get what i trade. please solve this problem.

And hope to reback my plat 1200+350. and 2 mods i trade tonight.