His Baseball Reference page mentions his purchase by the Athletics from the Browns, but not why Laabs ended up the 1947 on Detroit's AAA team in Buffalo.
This article in the July 8, 1948 Milwaukee Journal doesn't give us an exact date as to when a deal happened, but it does give us the reason Laabs was shuffled to Buffalo:
“One year ago Chet Laabs was railroaded out of the majors. Buffalo bought him for $10,000 from Connie Mack’s Philly A’s.”
Laabs was quite a homerun belter in that day, and he was doing the trick for Buffalo, leading to the "railroaded" editorial comment above. In reality, the then-35-year-olf Laabs had gotten off to a bad start with the A;s in 1947, hitting just .219 in 15 games.
After a few good productive years in Buffalo, Laabs was sent to the Toronto club in 1949. From the
July 8, 1949 Ottawa Journal:
“Toronto Maple Leafs of the International Baseball League announced yesterday outright purchase of outfielder Chet Laabs from Buffalo Bisons. Terms were not disclosed. Laabs. 35-year-old former major leaguer who played at one time with St. Louis Browns, Detroit Tigers and Philadelphia Athletics of the American League, batted .295 for Buffalo last season and drove in 81 runs. He bats and throws right-handed. Laabs will be on deck for tonight's Leafs-Rochester Red Wings game at Toronto.”
Laabs made one more AAA stop, Jersey City in 1950, but I haven't been able to find anything on that move. If you do, feel free to finish off this tale!