This attempts to reconnect any disconnected animCurve nodes found in a Maya scene. Written for Python 2.x. Adjust as needed for v3+

reconnectMayaAnimCurves.py

import maya.cmds as mc

def findNodeAndAttribute(animCurve):
    parts = animCurve.split("_")
    for index in range(len(parts)):
        node = "_".join(parts[:index + 1])
        attribute = "_".join(parts[index + 1:])
        # Look for the node
        # If it exists, look for the attribute
        if mc.objExists(node):
            attributes = mc.listAttr(node)
            # If the attribute exists, return both
            if attribute in attributes:
                return [node, attribute]
    return ["", ""]

for curveNode in mc.ls(type="animCurve"):
    # Find the node and attribute names
    node, attribute = findNodeAndAttribute(curveNode)
    if node == "":
        print "Unable to find a matching node for curve:", curveNode
        continue
    source = curveNode + ".output"
    destination = node + "." + attribute
    # Reconnect the animCurve to its attribute
    print "Connecting " + source + " to " + destination
    try:
        mc.connectAttr(source, destination)
    except:
        continue