The stamp is payment for the trip of the card, but you pay at the start. When a card goes abroad, the first mail service pays the next one for the rest of the journey.
If you send mail without or not enough stamps, most of the time, it will still be delivered, but at a loss for the first company.
In your case, it was paid. 
Today I received two postcards.
After 73 days an interesting postcard from China.
After 5 days a reproduction of an old postcard from France.
@tinkerstorm thank you so much for this beautiful card and informations about “The house of hunger” 
My İstanbul postcard has arrived to GUAM from TR🇹🇷
What a cutie! Love hedgehogs.
We sent out two cards today. Both are RAS cards going out to a little boy whose birthday is coming up soon. Eliza (my 8 year old this account is for) had a blast writing and decorating. Maybe I’ll post her mail art on another topic later.
Awwww! Adorable. Such good boys (or maybe they’re girls? 
) Either way, they’re super cute.
My postcard to USA has arrived!
Friday’s arrivals…
Thanks @SumireCecilia
My first ever mail from Mexico and 51st ( country or postal territory )
And on the way Missent to Thailand…
Thanks @tidorle
-my mail 6.4.: Official from BY
-my mail 01.04-05.04: Official from BR, Meetingcards from Silkie, Angel84 (DE), Dollart (FI) and Fisherman (IE), Holidaycard from Xioai (NL), Eastercards from Gabis, Durin, Joeyana and Loupe (DE), and surprisecards from Hoentje and Midnatsol (DE)
-sent today: Official to BY and surprisecards to FI and DE
-received a card from me: Bine2406, retlaw, Loupe Hoentje (DE), Bcsikar (RS) and Zachary (CA)
-Official cards travelling to: 
329 days Expired 
, 
301 days, 179 days Expired and 59 days, 
269 days Expired and today, 
252 days, Expired , 
132 days, Expired and 36 days, 
, 
8 days, 
and 
2 days.
-Last 10 received: , , , 
, 
, 
, , 
, 
and .
