@to4kawa Thank you for the help with your response! It took me awhile to get back to this, due to other projects. After many different variations of my logic I ended up only searching one index, which resolved my issue along with your suggestion. Below is the latest version of the script which is working as desired.
index=foo sourcetype=bar (OU="Vendor - Long Term" OR OU="Vendor - Short Term" OR OU="Vendor - VPN") lastLogonTimestamp*
| fields cn, lastLogonTimestamp, userPrincipalName, userAccountControl, accountExpires, OU,distinguishedName
| dedup cn
| rex field=distinguishedName "(?<AccountType>(?<=OU=)(.*)(?=,OU=Vendor))"
| eval last_logon = strptime(lastLogonTimestamp, "%H:%M.%S %p, %a %m/%d/%Y")
| where last_logon < relative_time(now(),"-14d@d")
| eval last_logon_date =strftime(strptime(lastLogonTimestamp,"%I:%M.%S %p, %a %m/%d/%Y"),"%Y/%m/%d")
| eval NetworkID = trim(replace(userPrincipalName, "@g1net.com", ""))
| eval uac = case(userAccountControl==66050,"Disabled, password never expires",userAccountControl==512,"Enable Account",userAccountControl==514,"Disable Account",userAccountControl==544,"Account Enabled - Require user to change password at first logon",userAccountControl==4096,"Workstation/Server",userAccountControl==66048,"Enabled, password never expires",userAccountControl==66050,"Disabled, password never expires",userAccountControl==262656,"Smart Card Logon Required",userAccountControl==532480,"Domain Controller",userAccountControl==1,"Script",userAccountControl==2,"Account Disabled",userAccountControl==16,"Locked Out",userAccountControl==512,"Normal Account",userAccountControl==8388608,"Password Expired",userAccountControl==8,"Home Directory Required",userAccountControl==32,"Password Not Require",userAccountControl==64,"Password Can't Change",userAccountControl==128,"Encrypted Text Password Allowed",userAccountControl==256,"Temp Duplicate Account",userAccountControl==2048,"Interdomain Trusted Account",userAccountControl==4096,"Workstation Tusted Account",userAccountControl==8192,"Server Trusted Account",userAccountControl==65536,"Don't Expire Password",userAccountControl==131072,"MNS Logon Account",userAccountControl==262144,"Smartcard Required",userAccountControl==524288,"Trusted for delegation",userAccountControl==1048576,"Not Delegated",userAccountControl==2097152,"Use Des Key Only",userAccountControl==4194304,"Don't Req Preauth",userAccountControl==16777216,"Trusted to auth for delegation")
| rename cn as "Name" NetworkID as "Network ID" AccountType as "Vendor Type" uac as "Account Status" last_logon_date as "Last Logon" accountExpires as "Account Expires"
| table "Network ID" Name "Vendor Type" "Last Logon" "Account Expires" "Account Status" | sort "Vendor Type", "Last Logon"
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