Yes, you are correct! As one accidentally deleted his important files from a memory card or hard drive, data recovery software really could help restore all his needed data back, provided that he has not saved anything new on this card or hard drive.
But, there are various data recovery programs on the market. And not all of them could be as efficient as we think.
Therefore, you could also try to retrieve your deleted files for free at the help of a memory card data recovery freeware, which has ever successfully restored the data of my friend form a mistakenly formatted Samsung phone memory card. Therefore, it is worth a shot.
Note: In case of similar troubles, you should remember to back up everything important all the time.