What is the ruling if a person puts a love padlock in certain places with the hopes of meeting his/her partner or so to have eternal love with their significant other?
A sincere love comes from a heart that puts everything for the feeling of dependence towards Allah SWT as His slave. True love doesn’t come from shirk and superstitious acts towards Him. None could benefit or harm except Allah SWT. Allah SWT states:
وَإِن يَمْسَسْكَ اللَّـهُ بِضُرٍّ فَلَا كَاشِفَ لَهُ إِلَّا هُوَ ۖ وَإِن يُرِدْكَ بِخَيْرٍ فَلَا رَادَّ لِفَضْلِهِ ۚ يُصِيبُ بِهِ مَن يَشَاءُ مِنْ عِبَادِهِ ۚ وَهُوَ الْغَفُورُ الرَّحِيمُ
“And if Allah should touch you with adversity, there is no remover of it except Him; and if He intends for you good, then there is no repeller of His bounty. He causes it to reach whom He wills of His servants. And He is the Forgiving, the Merciful,” 
Ibn Kathir said: “Indeed, goodness, calamity, benefit and dangers are all owned by Allah SWT. None disobey Him. Hence, Allah is the Only One that should be worshipped. None is like Him.” 
Believing that a love padlock would be able to grant eternal love and lock the love of a person with his partner is included in tiyarah or tatayyur. From Abdullah bin Mas’ud RA, the Messenger PBUH said:
الطِّيَرَةُ شِرْكٌ، الطِّيَرَةُ شِرْكٌ ، ثَلاَثًا ، وَمَا مِنَّا إِلاَّ وَلَكِنَّ اللَّهَ يُذْهِبُهُ بِالتَّوَكُّلِ.
“Taking evil omens is polytheism (saying it three times). None of us fails to be affected by it, but God removes such influence by trust in Him.” 
According to Ibn al-Qayyim, “The term tatayyur or tiyarah originated from the word al-tayr (الطير) which means bird. In the belief of the ancient Jahiliyah Arabs, when they wanted to go on a journey, they would first release birds. If the birds fly to the right, then it is considered as sa’ih, they’ll rejoice and continue to go on the journey. Consequently, if they flew to the left which is barih, then it means barih or bad luck and they’ll feel sad for it is a sign that a disaster will strike them and they would then postpone their journey.” 
It is prohibited to place a love padlock with the hopes that one will be able to find his significant other or have an everlasting love with his lover. Pray to the owner of hearts which is Allah SWT and strive to follow the limitations set by syarak to get the love that can get him closer to Allah SWT. Wallahu a’lam.