Kunci kamar saya tertinggal di meja resepsionis hotel.

Indonesian possession is usually shown by putting the possessor after the noun:

• kunci = key
• kamar = room
• kamar saya = my room (literally room my)
  So kunci kamar saya is literally “the key of my room”, i.e. my room key.
  Putting saya before the noun (saya kunci kamar) doesn’t work for possession in standard Indonesian.

Both can be used for “left behind/forgotten,” but the feel can differ:

• tertinggal: emphasizes that something was left behind at a location (it “remained there”).
• ketinggalan: often emphasizes that you failed to bring it along (you “got left without it”), and is very common in everyday speech.

In many real situations, both sound natural:

• Kunci kamar saya tertinggal di resepsionis.
• Kunci kamar saya ketinggalan di resepsionis.

Yes. Indonesian allows flexible word order depending on what you want to emphasize:

• Kunci kamar saya tertinggal di meja resepsionis hotel. (topic = the key)
• Saya meninggalkan kunci kamar saya di meja resepsionis hotel. (topic = I; more deliberate/neutral)
• Saya ketinggalan kunci kamar saya di meja resepsionis hotel. (topic = I; common, clearly accidental in everyday speech)

Note: Saya tertinggal kunci... is less natural for this meaning; tertinggal usually describes the object being left behind, not the person “leaving” it.

• meninggalkan = to leave something behind / to leave something somewhere (can be intentional or just neutral)
• tertinggal = implies it happened unintentionally (you didn’t mean to leave it)

So if you’re reporting a problem to hotel staff, tertinggal is often the more appropriate tone.

di marks a location where something is/was:

• di meja resepsionis = on/at the reception desk

ke indicates movement toward a place:

• ke meja resepsionis = to the reception desk
  That would sound like the key moved there (or someone brought it there), not that it was left there.

di meja is literally “on the table/desk”. In context, meja resepsionis is the front desk counter, so it naturally means on/at the hotel reception desk.

If you want to be extra specific about “on top of,” you can say:

• di atas meja resepsionis hotel = on top of the hotel reception desk

resepsionis can refer to:

• the receptionist (person), or
• the reception/front desk area (place), depending on context.

Because you have meja (desk), meja resepsionis clearly points to the front desk counter, not the person.

It’s a noun chain:

• meja = desk/table
• resepsionis = reception/front desk
• hotel = hotel

So meja resepsionis hotel = the hotel’s reception desk. Indonesian often stacks nouns like this without extra words like ’s.

You can specify quantity or pluralize:

• Dua kunci kamar saya tertinggal di meja resepsionis hotel. = My two room keys were left at the front desk.
• Kunci-kunci kamar saya tertinggal ... = My room keys (plural) were left ... (more general)