I had lost few of my data from my Android phone's memory card I'm using gionee marathon M3 with android 4.4.2. I had purchased Sony Micro sd HC UHS-1 class-10 memory card(Purchased from PayTM) of 32GB.

I had downloaded this card with 15 gb of data using card reader. Then I had taken more videos and songs from my friends device using xender. Later I had also downloaded videos from whatsapp and web. And once I also attached it to pc using data cable and downloaded few photos into it. Finally it have data of 25gb inside it.

After three days, when I go to file manager, I had shown that My card had lost few data from it (Approx 10 gb) and there present other data as it is. The lost data or files became 0 bytes in size automatically.

I had checked for data by connecting memory card by card reader to pc, still lost files are of 0 bytes. I had connected my phone to pc using data cable, still the lost files are of 0 bytes.

Why is this happen? Is there any problem with memory card or with it's class, or with phone or with memory card's size? My phone supports memory card upto 128GB. Please tell me what to do? Should I purchase memory card of 16GB or of 32GB having class 4? And also please tell me about recovering this data(Videos, Pictures)

Please help me with this.
Its most likely a one time issue. No, you don't need to run and buy a new SD card. There is a high chance that the issue was with your phone or a rogue app on it.
Also, always back up your data to prevent a major loss.
Its hard and many times costly to recover data from Flash drive unlike a hard drive. I would suggest you let go and if preferable format the SD card and forget about it.

Its a problem if this happens again anytime soon. Also check your apps to see if you don't have any rogue app or a pirated app.