Question about "received" transaction

[J E]

From the TSN contract cards, I was reconstructing the roster changes for the first Mets minor league team in 1961, the AA Mobile Bears. 

Towards the end of the season, the roster seemed to be getting pretty slim, down to 12 players. After checking the last 4 boxscores of the season however, I noticed that 3 players who the contract cards had listed as no longer on the team were still playing games.

I was thinking "rec" was recalled but I now see the term means "received" on the contract cards. What exactly does the "received" transaction mean, since it does not seem to mean the player leaves the team (they seem to only involve players on option). Is it some other roster status change but the player still remains with the same club?

The 3 players in question are:

Joyner White (received by Dallas 8/25/61)

Ed Drapcho (received by Chicago AL 8/30/61)

Bobby Joe Case (received by San Diego 8/31/61)

All three of these players however continued playing games for Mobile until its final game of the season on 9/4/61.

Thanks for any help you can provide!