I have been able to find one instance of Bradman being stumped, by Duckworth off verity for 132 in 1934 playing for Australia vs HDG Levenson-Gower XI.
Considering that he was stumped 11 times in first class games in his career, I doubt if Duckworth stumped him everytime.
For example in 1927-28 he was stumped in the game against Victoria in the sheffield shield. Probably his first such dismissal in first class cricket.
Sheffield Shield, 1927/28
New South Wales v Victoria
Sydney Cricket Ground
26,27,28,30,31 January 1928 (5-day match)
Result: Match drawn
Toss: New South Wales
Umpires: WG French and AC Jones
Balls per over: 8
Close of play:
Day 1: New South Wales 349/7 (Oldfield 18*, Nicholls 39*)
Day 2: New South Wales 533, Victoria 158/1 (Woodfull 74*, Hendry 73*)
Day 3: Victoria 422, New South Wales 0/0 (Phillips 0*, Jackson 0*)
Day 4: New South Wales 353/8 (Bradman 134*, Mailey 11*)
New South Wales 1st innings
JM Gregory lbw b Morton 12
A Jackson c Hendry b a'Beckett 11
TJE Andrews c & b Morton 4
*AF Kippax b a'Beckett 134
JG Morgan b Blackie 110
DG Bradman st Ellis b Blackie 7
NE Phillips lbw b a'Beckett 0
+WAS Oldfield c sub (AJW Lansdown) b a'Beckett 101
CO Nicholls b a'Beckett 110
AA Mailey b a'Beckett 12
RLA McNamee not out 8
Extras (b 16, lb 1, w 1, nb 6) 24
Total (all out, 123.6 overs, 476 mins) 533
FoW: 1-25, 2-25, 3-31, 4-276, 5-290,
6-291, 7-291, 8-495, 9-510, 10-533.