The payment to the user was made using two inputs:
"txid" : "acd552f807f0eeb3c0a3ddd852c5042c9b354b73b5c547310808be7825837a6b", "vout" : 1
"txid" : "e87eefbcfb9530de343044464cf38e4d0d287ad9719cee03063868d00217a157", "vout" : 1
Note this is all we care about. The amount of the inputs are not needed. If these inputs are in are found in a tx to the user in a block regardless of the tx hash then the user has been paid.
One can simply record this information and wait until he gets complaints.
Normally there is no need to do anything. When a complaint is received, knowing inputs he can check whether these inputs are spent, and thus determine if complaint is valid or not. (If it is a valid complaint things become tricky, at that point consultation with specialists might be necessary as bitcoind won't just forget about wallet transactions.)
If you want an automatic sanity checker, the easiest way is to lookup spends of these coins via some kind of a block explorer API, in this case it might be just like a dozen lines of code. If you don't trust external block explorer, run your own ABE instance.
Processing block data like DeathAndTaxes described is also an option, but requires more code