Can phone be hacked to dismount SD card?

I tried to look at my SD card and got an error message that it was dismounted. Just before that I received two very large "multi-media" text messages. I don't know what a "multi-media" text message is - and the phone says they couldn't be downloaded.

Could these be from someone trying to hack into my phone - and then dismounting the SD card?

>>>UPDATE<<<
I just discovered that sometimes, depending upon what android feels like showing, after pulling down SD Card available from to of screen, there are "Explore" and "Eject" choices at the bottom of the screen right next to each other! Because of that terrible proximity - they should be on opposite sides of the screen!! - it is quite easy to accidentally press "Eject" instead of pressing "Explore". I expect that is what happened.

However, I still want to know what "multi-media" text messages are and wheher I should try to download them (though android wasn't able to download them).

 

Thank you ocnbrze. I edited my original post - obviously after you read it and replied - and explained what I believe happened. And you're right - I'll relax
And I appreciate your explanation of mms message. I'll just deleted the notifications in the text message list.