Consider transaction 0846e91bc3afdf2275db14bcbb10e19f141069d77f17dae6bcbd907fd28f4747, which takes money out of the script address 3PJQGGnBQr8DJBdPYowd6Mp2kSWvFFo7Gk. As we can see in the input scripts, this script address references script 51210261afd7a2796e9bb83896089293f11edd2987ebbd67ed2075f5e45b7c4bb7edcb51ae, which, according to the decodescript command, is

    "asm": "1 0261afd7a2796e9bb83896089293f11edd2987ebbd67ed2075f5e45b7c4bb7edcb 1 OP_CHECKMULTISIG",     "reqSigs": 1,     "type": "multisig",     "addresses": [         "1xW3APNVG6Ro1HY8hysmnKq8mvgVk6oPU"     ],     "p2sh": "3PJQGGnBQr8DJBdPYowd6Mp2kSWvFFo7Gk" 

So this payment was made to anyone who has access to the key with the address 1xW3APNVG6Ro1HY8hysmnKq8mvgVk6oPU.

But none of the common block explorer websites seem to index this; when I ask them about the address 1xW3APNVG6Ro1HY8hysmnKq8mvgVk6oPU, they list no transactions.

Is there a block explorer that maintains a mapping from key address to the script addresses the key is mentioned in?